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3075 lines
84 KiB
3075 lines
84 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* linux/mm/compaction.c |
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* |
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* Memory compaction for the reduction of external fragmentation. Note that |
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* this heavily depends upon page migration to do all the real heavy |
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* lifting |
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* |
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* Copyright IBM Corp. 2007-2010 Mel Gorman <[email protected]> |
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*/ |
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#include <linux/cpu.h> |
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#include <linux/swap.h> |
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#include <linux/migrate.h> |
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#include <linux/compaction.h> |
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#include <linux/mm_inline.h> |
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#include <linux/sched/signal.h> |
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#include <linux/backing-dev.h> |
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#include <linux/sysctl.h> |
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#include <linux/sysfs.h> |
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#include <linux/page-isolation.h> |
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#include <linux/kasan.h> |
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#include <linux/kthread.h> |
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#include <linux/freezer.h> |
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#include <linux/page_owner.h> |
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#include <linux/psi.h> |
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#include "internal.h" |
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|
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#ifdef CONFIG_COMPACTION |
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/* |
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* Fragmentation score check interval for proactive compaction purposes. |
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*/ |
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#define HPAGE_FRAG_CHECK_INTERVAL_MSEC (500) |
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|
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static inline void count_compact_event(enum vm_event_item item) |
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{ |
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count_vm_event(item); |
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} |
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|
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static inline void count_compact_events(enum vm_event_item item, long delta) |
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{ |
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count_vm_events(item, delta); |
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} |
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#else |
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#define count_compact_event(item) do { } while (0) |
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#define count_compact_events(item, delta) do { } while (0) |
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#endif |
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|
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#if defined CONFIG_COMPACTION || defined CONFIG_CMA |
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|
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#define CREATE_TRACE_POINTS |
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#include <trace/events/compaction.h> |
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|
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#define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order)) |
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#define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order)) |
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|
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/* |
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* Page order with-respect-to which proactive compaction |
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* calculates external fragmentation, which is used as |
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* the "fragmentation score" of a node/zone. |
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*/ |
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#if defined CONFIG_TRANSPARENT_HUGEPAGE |
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#define COMPACTION_HPAGE_ORDER HPAGE_PMD_ORDER |
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#elif defined CONFIG_HUGETLBFS |
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#define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER |
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#else |
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#define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT) |
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#endif |
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|
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static unsigned long release_freepages(struct list_head *freelist) |
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{ |
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struct page *page, *next; |
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unsigned long high_pfn = 0; |
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|
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list_for_each_entry_safe(page, next, freelist, lru) { |
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unsigned long pfn = page_to_pfn(page); |
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list_del(&page->lru); |
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__free_page(page); |
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if (pfn > high_pfn) |
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high_pfn = pfn; |
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} |
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|
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return high_pfn; |
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} |
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|
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static void split_map_pages(struct list_head *list) |
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{ |
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unsigned int i, order, nr_pages; |
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struct page *page, *next; |
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LIST_HEAD(tmp_list); |
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|
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list_for_each_entry_safe(page, next, list, lru) { |
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list_del(&page->lru); |
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|
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order = page_private(page); |
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nr_pages = 1 << order; |
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|
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post_alloc_hook(page, order, __GFP_MOVABLE); |
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if (order) |
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split_page(page, order); |
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|
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for (i = 0; i < nr_pages; i++) { |
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list_add(&page->lru, &tmp_list); |
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page++; |
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} |
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} |
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|
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list_splice(&tmp_list, list); |
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} |
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|
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#ifdef CONFIG_COMPACTION |
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bool PageMovable(struct page *page) |
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{ |
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const struct movable_operations *mops; |
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|
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VM_BUG_ON_PAGE(!PageLocked(page), page); |
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if (!__PageMovable(page)) |
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return false; |
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|
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mops = page_movable_ops(page); |
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if (mops) |
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return true; |
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|
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return false; |
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} |
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EXPORT_SYMBOL(PageMovable); |
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|
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void __SetPageMovable(struct page *page, const struct movable_operations *mops) |
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{ |
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VM_BUG_ON_PAGE(!PageLocked(page), page); |
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VM_BUG_ON_PAGE((unsigned long)mops & PAGE_MAPPING_MOVABLE, page); |
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page->mapping = (void *)((unsigned long)mops | PAGE_MAPPING_MOVABLE); |
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} |
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EXPORT_SYMBOL(__SetPageMovable); |
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|
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void __ClearPageMovable(struct page *page) |
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{ |
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VM_BUG_ON_PAGE(!PageMovable(page), page); |
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/* |
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* This page still has the type of a movable page, but it's |
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* actually not movable any more. |
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*/ |
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page->mapping = (void *)PAGE_MAPPING_MOVABLE; |
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} |
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EXPORT_SYMBOL(__ClearPageMovable); |
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|
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/* Do not skip compaction more than 64 times */ |
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#define COMPACT_MAX_DEFER_SHIFT 6 |
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|
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/* |
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* Compaction is deferred when compaction fails to result in a page |
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* allocation success. 1 << compact_defer_shift, compactions are skipped up |
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* to a limit of 1 << COMPACT_MAX_DEFER_SHIFT |
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*/ |
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static void defer_compaction(struct zone *zone, int order) |
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{ |
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zone->compact_considered = 0; |
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zone->compact_defer_shift++; |
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|
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if (order < zone->compact_order_failed) |
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zone->compact_order_failed = order; |
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|
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if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT) |
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zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT; |
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|
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trace_mm_compaction_defer_compaction(zone, order); |
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} |
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|
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/* Returns true if compaction should be skipped this time */ |
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static bool compaction_deferred(struct zone *zone, int order) |
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{ |
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unsigned long defer_limit = 1UL << zone->compact_defer_shift; |
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|
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if (order < zone->compact_order_failed) |
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return false; |
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|
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/* Avoid possible overflow */ |
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if (++zone->compact_considered >= defer_limit) { |
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zone->compact_considered = defer_limit; |
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return false; |
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} |
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|
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trace_mm_compaction_deferred(zone, order); |
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|
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return true; |
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} |
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|
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/* |
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* Update defer tracking counters after successful compaction of given order, |
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* which means an allocation either succeeded (alloc_success == true) or is |
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* expected to succeed. |
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*/ |
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void compaction_defer_reset(struct zone *zone, int order, |
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bool alloc_success) |
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{ |
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if (alloc_success) { |
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zone->compact_considered = 0; |
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zone->compact_defer_shift = 0; |
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} |
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if (order >= zone->compact_order_failed) |
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zone->compact_order_failed = order + 1; |
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|
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trace_mm_compaction_defer_reset(zone, order); |
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} |
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|
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/* Returns true if restarting compaction after many failures */ |
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static bool compaction_restarting(struct zone *zone, int order) |
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{ |
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if (order < zone->compact_order_failed) |
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return false; |
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|
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return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT && |
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zone->compact_considered >= 1UL << zone->compact_defer_shift; |
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} |
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|
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/* Returns true if the pageblock should be scanned for pages to isolate. */ |
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static inline bool isolation_suitable(struct compact_control *cc, |
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struct page *page) |
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{ |
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if (cc->ignore_skip_hint) |
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return true; |
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|
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return !get_pageblock_skip(page); |
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} |
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|
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static void reset_cached_positions(struct zone *zone) |
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{ |
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zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn; |
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zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn; |
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zone->compact_cached_free_pfn = |
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pageblock_start_pfn(zone_end_pfn(zone) - 1); |
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} |
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|
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/* |
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* Compound pages of >= pageblock_order should consistently be skipped until |
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* released. It is always pointless to compact pages of such order (if they are |
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* migratable), and the pageblocks they occupy cannot contain any free pages. |
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*/ |
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static bool pageblock_skip_persistent(struct page *page) |
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{ |
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if (!PageCompound(page)) |
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return false; |
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|
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page = compound_head(page); |
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|
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if (compound_order(page) >= pageblock_order) |
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return true; |
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return false; |
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} |
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|
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static bool |
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__reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source, |
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bool check_target) |
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{ |
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struct page *page = pfn_to_online_page(pfn); |
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struct page *block_page; |
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struct page *end_page; |
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unsigned long block_pfn; |
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if (!page) |
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return false; |
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if (zone != page_zone(page)) |
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return false; |
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if (pageblock_skip_persistent(page)) |
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return false; |
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|
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/* |
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* If skip is already cleared do no further checking once the |
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* restart points have been set. |
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*/ |
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if (check_source && check_target && !get_pageblock_skip(page)) |
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return true; |
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|
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/* |
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* If clearing skip for the target scanner, do not select a |
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* non-movable pageblock as the starting point. |
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*/ |
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if (!check_source && check_target && |
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get_pageblock_migratetype(page) != MIGRATE_MOVABLE) |
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return false; |
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|
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/* Ensure the start of the pageblock or zone is online and valid */ |
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block_pfn = pageblock_start_pfn(pfn); |
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block_pfn = max(block_pfn, zone->zone_start_pfn); |
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block_page = pfn_to_online_page(block_pfn); |
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if (block_page) { |
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page = block_page; |
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pfn = block_pfn; |
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} |
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|
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/* Ensure the end of the pageblock or zone is online and valid */ |
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block_pfn = pageblock_end_pfn(pfn) - 1; |
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block_pfn = min(block_pfn, zone_end_pfn(zone) - 1); |
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end_page = pfn_to_online_page(block_pfn); |
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if (!end_page) |
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return false; |
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|
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/* |
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* Only clear the hint if a sample indicates there is either a |
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* free page or an LRU page in the block. One or other condition |
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* is necessary for the block to be a migration source/target. |
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*/ |
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do { |
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if (check_source && PageLRU(page)) { |
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clear_pageblock_skip(page); |
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return true; |
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} |
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|
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if (check_target && PageBuddy(page)) { |
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clear_pageblock_skip(page); |
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return true; |
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} |
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page += (1 << PAGE_ALLOC_COSTLY_ORDER); |
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} while (page <= end_page); |
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|
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return false; |
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} |
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|
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/* |
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* This function is called to clear all cached information on pageblocks that |
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* should be skipped for page isolation when the migrate and free page scanner |
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* meet. |
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*/ |
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static void __reset_isolation_suitable(struct zone *zone) |
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{ |
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unsigned long migrate_pfn = zone->zone_start_pfn; |
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unsigned long free_pfn = zone_end_pfn(zone) - 1; |
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unsigned long reset_migrate = free_pfn; |
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unsigned long reset_free = migrate_pfn; |
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bool source_set = false; |
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bool free_set = false; |
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|
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if (!zone->compact_blockskip_flush) |
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return; |
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zone->compact_blockskip_flush = false; |
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|
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/* |
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* Walk the zone and update pageblock skip information. Source looks |
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* for PageLRU while target looks for PageBuddy. When the scanner |
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* is found, both PageBuddy and PageLRU are checked as the pageblock |
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* is suitable as both source and target. |
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*/ |
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for (; migrate_pfn < free_pfn; migrate_pfn += pageblock_nr_pages, |
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free_pfn -= pageblock_nr_pages) { |
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cond_resched(); |
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|
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/* Update the migrate PFN */ |
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if (__reset_isolation_pfn(zone, migrate_pfn, true, source_set) && |
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migrate_pfn < reset_migrate) { |
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source_set = true; |
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reset_migrate = migrate_pfn; |
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zone->compact_init_migrate_pfn = reset_migrate; |
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zone->compact_cached_migrate_pfn[0] = reset_migrate; |
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zone->compact_cached_migrate_pfn[1] = reset_migrate; |
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} |
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|
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/* Update the free PFN */ |
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if (__reset_isolation_pfn(zone, free_pfn, free_set, true) && |
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free_pfn > reset_free) { |
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free_set = true; |
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reset_free = free_pfn; |
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zone->compact_init_free_pfn = reset_free; |
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zone->compact_cached_free_pfn = reset_free; |
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} |
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} |
|
|
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/* Leave no distance if no suitable block was reset */ |
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if (reset_migrate >= reset_free) { |
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zone->compact_cached_migrate_pfn[0] = migrate_pfn; |
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zone->compact_cached_migrate_pfn[1] = migrate_pfn; |
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zone->compact_cached_free_pfn = free_pfn; |
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} |
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} |
|
|
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void reset_isolation_suitable(pg_data_t *pgdat) |
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{ |
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int zoneid; |
|
|
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for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
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struct zone *zone = &pgdat->node_zones[zoneid]; |
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if (!populated_zone(zone)) |
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continue; |
|
|
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/* Only flush if a full compaction finished recently */ |
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if (zone->compact_blockskip_flush) |
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__reset_isolation_suitable(zone); |
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} |
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} |
|
|
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/* |
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* Sets the pageblock skip bit if it was clear. Note that this is a hint as |
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* locks are not required for read/writers. Returns true if it was already set. |
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*/ |
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static bool test_and_set_skip(struct compact_control *cc, struct page *page, |
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unsigned long pfn) |
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{ |
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bool skip; |
|
|
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/* Do no update if skip hint is being ignored */ |
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if (cc->ignore_skip_hint) |
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return false; |
|
|
|
if (!pageblock_aligned(pfn)) |
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return false; |
|
|
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skip = get_pageblock_skip(page); |
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if (!skip && !cc->no_set_skip_hint) |
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set_pageblock_skip(page); |
|
|
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return skip; |
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} |
|
|
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static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) |
|
{ |
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struct zone *zone = cc->zone; |
|
|
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pfn = pageblock_end_pfn(pfn); |
|
|
|
/* Set for isolation rather than compaction */ |
|
if (cc->no_set_skip_hint) |
|
return; |
|
|
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if (pfn > zone->compact_cached_migrate_pfn[0]) |
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zone->compact_cached_migrate_pfn[0] = pfn; |
|
if (cc->mode != MIGRATE_ASYNC && |
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pfn > zone->compact_cached_migrate_pfn[1]) |
|
zone->compact_cached_migrate_pfn[1] = pfn; |
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} |
|
|
|
/* |
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* If no pages were isolated then mark this pageblock to be skipped in the |
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* future. The information is later cleared by __reset_isolation_suitable(). |
|
*/ |
|
static void update_pageblock_skip(struct compact_control *cc, |
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struct page *page, unsigned long pfn) |
|
{ |
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struct zone *zone = cc->zone; |
|
|
|
if (cc->no_set_skip_hint) |
|
return; |
|
|
|
if (!page) |
|
return; |
|
|
|
set_pageblock_skip(page); |
|
|
|
/* Update where async and sync compaction should restart */ |
|
if (pfn < zone->compact_cached_free_pfn) |
|
zone->compact_cached_free_pfn = pfn; |
|
} |
|
#else |
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static inline bool isolation_suitable(struct compact_control *cc, |
|
struct page *page) |
|
{ |
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return true; |
|
} |
|
|
|
static inline bool pageblock_skip_persistent(struct page *page) |
|
{ |
|
return false; |
|
} |
|
|
|
static inline void update_pageblock_skip(struct compact_control *cc, |
|
struct page *page, unsigned long pfn) |
|
{ |
|
} |
|
|
|
static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) |
|
{ |
|
} |
|
|
|
static bool test_and_set_skip(struct compact_control *cc, struct page *page, |
|
unsigned long pfn) |
|
{ |
|
return false; |
|
} |
|
#endif /* CONFIG_COMPACTION */ |
|
|
|
/* |
|
* Compaction requires the taking of some coarse locks that are potentially |
|
* very heavily contended. For async compaction, trylock and record if the |
|
* lock is contended. The lock will still be acquired but compaction will |
|
* abort when the current block is finished regardless of success rate. |
|
* Sync compaction acquires the lock. |
|
* |
|
* Always returns true which makes it easier to track lock state in callers. |
|
*/ |
|
static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags, |
|
struct compact_control *cc) |
|
__acquires(lock) |
|
{ |
|
/* Track if the lock is contended in async mode */ |
|
if (cc->mode == MIGRATE_ASYNC && !cc->contended) { |
|
if (spin_trylock_irqsave(lock, *flags)) |
|
return true; |
|
|
|
cc->contended = true; |
|
} |
|
|
|
spin_lock_irqsave(lock, *flags); |
|
return true; |
|
} |
|
|
|
/* |
|
* Compaction requires the taking of some coarse locks that are potentially |
|
* very heavily contended. The lock should be periodically unlocked to avoid |
|
* having disabled IRQs for a long time, even when there is nobody waiting on |
|
* the lock. It might also be that allowing the IRQs will result in |
|
* need_resched() becoming true. If scheduling is needed, compaction schedules. |
|
* Either compaction type will also abort if a fatal signal is pending. |
|
* In either case if the lock was locked, it is dropped and not regained. |
|
* |
|
* Returns true if compaction should abort due to fatal signal pending. |
|
* Returns false when compaction can continue. |
|
*/ |
|
static bool compact_unlock_should_abort(spinlock_t *lock, |
|
unsigned long flags, bool *locked, struct compact_control *cc) |
|
{ |
|
if (*locked) { |
|
spin_unlock_irqrestore(lock, flags); |
|
*locked = false; |
|
} |
|
|
|
if (fatal_signal_pending(current)) { |
|
cc->contended = true; |
|
return true; |
|
} |
|
|
|
cond_resched(); |
|
|
|
return false; |
|
} |
|
|
|
/* |
|
* Isolate free pages onto a private freelist. If @strict is true, will abort |
|
* returning 0 on any invalid PFNs or non-free pages inside of the pageblock |
|
* (even though it may still end up isolating some pages). |
|
*/ |
|
static unsigned long isolate_freepages_block(struct compact_control *cc, |
|
unsigned long *start_pfn, |
|
unsigned long end_pfn, |
|
struct list_head *freelist, |
|
unsigned int stride, |
|
bool strict) |
|
{ |
|
int nr_scanned = 0, total_isolated = 0; |
|
struct page *cursor; |
|
unsigned long flags = 0; |
|
bool locked = false; |
|
unsigned long blockpfn = *start_pfn; |
|
unsigned int order; |
|
|
|
/* Strict mode is for isolation, speed is secondary */ |
|
if (strict) |
|
stride = 1; |
|
|
|
cursor = pfn_to_page(blockpfn); |
|
|
|
/* Isolate free pages. */ |
|
for (; blockpfn < end_pfn; blockpfn += stride, cursor += stride) { |
|
int isolated; |
|
struct page *page = cursor; |
|
|
|
/* |
|
* Periodically drop the lock (if held) regardless of its |
|
* contention, to give chance to IRQs. Abort if fatal signal |
|
* pending. |
|
*/ |
|
if (!(blockpfn % COMPACT_CLUSTER_MAX) |
|
&& compact_unlock_should_abort(&cc->zone->lock, flags, |
|
&locked, cc)) |
|
break; |
|
|
|
nr_scanned++; |
|
|
|
/* |
|
* For compound pages such as THP and hugetlbfs, we can save |
|
* potentially a lot of iterations if we skip them at once. |
|
* The check is racy, but we can consider only valid values |
|
* and the only danger is skipping too much. |
|
*/ |
|
if (PageCompound(page)) { |
|
const unsigned int order = compound_order(page); |
|
|
|
if (likely(order < MAX_ORDER)) { |
|
blockpfn += (1UL << order) - 1; |
|
cursor += (1UL << order) - 1; |
|
} |
|
goto isolate_fail; |
|
} |
|
|
|
if (!PageBuddy(page)) |
|
goto isolate_fail; |
|
|
|
/* If we already hold the lock, we can skip some rechecking. */ |
|
if (!locked) { |
|
locked = compact_lock_irqsave(&cc->zone->lock, |
|
&flags, cc); |
|
|
|
/* Recheck this is a buddy page under lock */ |
|
if (!PageBuddy(page)) |
|
goto isolate_fail; |
|
} |
|
|
|
/* Found a free page, will break it into order-0 pages */ |
|
order = buddy_order(page); |
|
isolated = __isolate_free_page(page, order); |
|
if (!isolated) |
|
break; |
|
set_page_private(page, order); |
|
|
|
nr_scanned += isolated - 1; |
|
total_isolated += isolated; |
|
cc->nr_freepages += isolated; |
|
list_add_tail(&page->lru, freelist); |
|
|
|
if (!strict && cc->nr_migratepages <= cc->nr_freepages) { |
|
blockpfn += isolated; |
|
break; |
|
} |
|
/* Advance to the end of split page */ |
|
blockpfn += isolated - 1; |
|
cursor += isolated - 1; |
|
continue; |
|
|
|
isolate_fail: |
|
if (strict) |
|
break; |
|
else |
|
continue; |
|
|
|
} |
|
|
|
if (locked) |
|
spin_unlock_irqrestore(&cc->zone->lock, flags); |
|
|
|
/* |
|
* There is a tiny chance that we have read bogus compound_order(), |
|
* so be careful to not go outside of the pageblock. |
|
*/ |
|
if (unlikely(blockpfn > end_pfn)) |
|
blockpfn = end_pfn; |
|
|
|
trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn, |
|
nr_scanned, total_isolated); |
|
|
|
/* Record how far we have got within the block */ |
|
*start_pfn = blockpfn; |
|
|
|
/* |
|
* If strict isolation is requested by CMA then check that all the |
|
* pages requested were isolated. If there were any failures, 0 is |
|
* returned and CMA will fail. |
|
*/ |
|
if (strict && blockpfn < end_pfn) |
|
total_isolated = 0; |
|
|
|
cc->total_free_scanned += nr_scanned; |
|
if (total_isolated) |
|
count_compact_events(COMPACTISOLATED, total_isolated); |
|
return total_isolated; |
|
} |
|
|
|
/** |
|
* isolate_freepages_range() - isolate free pages. |
|
* @cc: Compaction control structure. |
|
* @start_pfn: The first PFN to start isolating. |
|
* @end_pfn: The one-past-last PFN. |
|
* |
|
* Non-free pages, invalid PFNs, or zone boundaries within the |
|
* [start_pfn, end_pfn) range are considered errors, cause function to |
|
* undo its actions and return zero. |
|
* |
|
* Otherwise, function returns one-past-the-last PFN of isolated page |
|
* (which may be greater then end_pfn if end fell in a middle of |
|
* a free page). |
|
*/ |
|
unsigned long |
|
isolate_freepages_range(struct compact_control *cc, |
|
unsigned long start_pfn, unsigned long end_pfn) |
|
{ |
|
unsigned long isolated, pfn, block_start_pfn, block_end_pfn; |
|
LIST_HEAD(freelist); |
|
|
|
pfn = start_pfn; |
|
block_start_pfn = pageblock_start_pfn(pfn); |
|
if (block_start_pfn < cc->zone->zone_start_pfn) |
|
block_start_pfn = cc->zone->zone_start_pfn; |
|
block_end_pfn = pageblock_end_pfn(pfn); |
|
|
|
for (; pfn < end_pfn; pfn += isolated, |
|
block_start_pfn = block_end_pfn, |
|
block_end_pfn += pageblock_nr_pages) { |
|
/* Protect pfn from changing by isolate_freepages_block */ |
|
unsigned long isolate_start_pfn = pfn; |
|
|
|
block_end_pfn = min(block_end_pfn, end_pfn); |
|
|
|
/* |
|
* pfn could pass the block_end_pfn if isolated freepage |
|
* is more than pageblock order. In this case, we adjust |
|
* scanning range to right one. |
|
*/ |
|
if (pfn >= block_end_pfn) { |
|
block_start_pfn = pageblock_start_pfn(pfn); |
|
block_end_pfn = pageblock_end_pfn(pfn); |
|
block_end_pfn = min(block_end_pfn, end_pfn); |
|
} |
|
|
|
if (!pageblock_pfn_to_page(block_start_pfn, |
|
block_end_pfn, cc->zone)) |
|
break; |
|
|
|
isolated = isolate_freepages_block(cc, &isolate_start_pfn, |
|
block_end_pfn, &freelist, 0, true); |
|
|
|
/* |
|
* In strict mode, isolate_freepages_block() returns 0 if |
|
* there are any holes in the block (ie. invalid PFNs or |
|
* non-free pages). |
|
*/ |
|
if (!isolated) |
|
break; |
|
|
|
/* |
|
* If we managed to isolate pages, it is always (1 << n) * |
|
* pageblock_nr_pages for some non-negative n. (Max order |
|
* page may span two pageblocks). |
|
*/ |
|
} |
|
|
|
/* __isolate_free_page() does not map the pages */ |
|
split_map_pages(&freelist); |
|
|
|
if (pfn < end_pfn) { |
|
/* Loop terminated early, cleanup. */ |
|
release_freepages(&freelist); |
|
return 0; |
|
} |
|
|
|
/* We don't use freelists for anything. */ |
|
return pfn; |
|
} |
|
|
|
/* Similar to reclaim, but different enough that they don't share logic */ |
|
static bool too_many_isolated(pg_data_t *pgdat) |
|
{ |
|
bool too_many; |
|
|
|
unsigned long active, inactive, isolated; |
|
|
|
inactive = node_page_state(pgdat, NR_INACTIVE_FILE) + |
|
node_page_state(pgdat, NR_INACTIVE_ANON); |
|
active = node_page_state(pgdat, NR_ACTIVE_FILE) + |
|
node_page_state(pgdat, NR_ACTIVE_ANON); |
|
isolated = node_page_state(pgdat, NR_ISOLATED_FILE) + |
|
node_page_state(pgdat, NR_ISOLATED_ANON); |
|
|
|
too_many = isolated > (inactive + active) / 2; |
|
if (!too_many) |
|
wake_throttle_isolated(pgdat); |
|
|
|
return too_many; |
|
} |
|
|
|
/** |
|
* isolate_migratepages_block() - isolate all migrate-able pages within |
|
* a single pageblock |
|
* @cc: Compaction control structure. |
|
* @low_pfn: The first PFN to isolate |
|
* @end_pfn: The one-past-the-last PFN to isolate, within same pageblock |
|
* @mode: Isolation mode to be used. |
|
* |
|
* Isolate all pages that can be migrated from the range specified by |
|
* [low_pfn, end_pfn). The range is expected to be within same pageblock. |
|
* Returns errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion, |
|
* -ENOMEM in case we could not allocate a page, or 0. |
|
* cc->migrate_pfn will contain the next pfn to scan. |
|
* |
|
* The pages are isolated on cc->migratepages list (not required to be empty), |
|
* and cc->nr_migratepages is updated accordingly. |
|
*/ |
|
static int |
|
isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, |
|
unsigned long end_pfn, isolate_mode_t mode) |
|
{ |
|
pg_data_t *pgdat = cc->zone->zone_pgdat; |
|
unsigned long nr_scanned = 0, nr_isolated = 0; |
|
struct lruvec *lruvec; |
|
unsigned long flags = 0; |
|
struct lruvec *locked = NULL; |
|
struct page *page = NULL, *valid_page = NULL; |
|
struct address_space *mapping; |
|
unsigned long start_pfn = low_pfn; |
|
bool skip_on_failure = false; |
|
unsigned long next_skip_pfn = 0; |
|
bool skip_updated = false; |
|
int ret = 0; |
|
|
|
cc->migrate_pfn = low_pfn; |
|
|
|
/* |
|
* Ensure that there are not too many pages isolated from the LRU |
|
* list by either parallel reclaimers or compaction. If there are, |
|
* delay for some time until fewer pages are isolated |
|
*/ |
|
while (unlikely(too_many_isolated(pgdat))) { |
|
/* stop isolation if there are still pages not migrated */ |
|
if (cc->nr_migratepages) |
|
return -EAGAIN; |
|
|
|
/* async migration should just abort */ |
|
if (cc->mode == MIGRATE_ASYNC) |
|
return -EAGAIN; |
|
|
|
reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED); |
|
|
|
if (fatal_signal_pending(current)) |
|
return -EINTR; |
|
} |
|
|
|
cond_resched(); |
|
|
|
if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) { |
|
skip_on_failure = true; |
|
next_skip_pfn = block_end_pfn(low_pfn, cc->order); |
|
} |
|
|
|
/* Time to isolate some pages for migration */ |
|
for (; low_pfn < end_pfn; low_pfn++) { |
|
|
|
if (skip_on_failure && low_pfn >= next_skip_pfn) { |
|
/* |
|
* We have isolated all migration candidates in the |
|
* previous order-aligned block, and did not skip it due |
|
* to failure. We should migrate the pages now and |
|
* hopefully succeed compaction. |
|
*/ |
|
if (nr_isolated) |
|
break; |
|
|
|
/* |
|
* We failed to isolate in the previous order-aligned |
|
* block. Set the new boundary to the end of the |
|
* current block. Note we can't simply increase |
|
* next_skip_pfn by 1 << order, as low_pfn might have |
|
* been incremented by a higher number due to skipping |
|
* a compound or a high-order buddy page in the |
|
* previous loop iteration. |
|
*/ |
|
next_skip_pfn = block_end_pfn(low_pfn, cc->order); |
|
} |
|
|
|
/* |
|
* Periodically drop the lock (if held) regardless of its |
|
* contention, to give chance to IRQs. Abort completely if |
|
* a fatal signal is pending. |
|
*/ |
|
if (!(low_pfn % COMPACT_CLUSTER_MAX)) { |
|
if (locked) { |
|
unlock_page_lruvec_irqrestore(locked, flags); |
|
locked = NULL; |
|
} |
|
|
|
if (fatal_signal_pending(current)) { |
|
cc->contended = true; |
|
ret = -EINTR; |
|
|
|
goto fatal_pending; |
|
} |
|
|
|
cond_resched(); |
|
} |
|
|
|
nr_scanned++; |
|
|
|
page = pfn_to_page(low_pfn); |
|
|
|
/* |
|
* Check if the pageblock has already been marked skipped. |
|
* Only the aligned PFN is checked as the caller isolates |
|
* COMPACT_CLUSTER_MAX at a time so the second call must |
|
* not falsely conclude that the block should be skipped. |
|
*/ |
|
if (!valid_page && pageblock_aligned(low_pfn)) { |
|
if (!isolation_suitable(cc, page)) { |
|
low_pfn = end_pfn; |
|
page = NULL; |
|
goto isolate_abort; |
|
} |
|
valid_page = page; |
|
} |
|
|
|
if (PageHuge(page) && cc->alloc_contig) { |
|
ret = isolate_or_dissolve_huge_page(page, &cc->migratepages); |
|
|
|
/* |
|
* Fail isolation in case isolate_or_dissolve_huge_page() |
|
* reports an error. In case of -ENOMEM, abort right away. |
|
*/ |
|
if (ret < 0) { |
|
/* Do not report -EBUSY down the chain */ |
|
if (ret == -EBUSY) |
|
ret = 0; |
|
low_pfn += compound_nr(page) - 1; |
|
goto isolate_fail; |
|
} |
|
|
|
if (PageHuge(page)) { |
|
/* |
|
* Hugepage was successfully isolated and placed |
|
* on the cc->migratepages list. |
|
*/ |
|
low_pfn += compound_nr(page) - 1; |
|
goto isolate_success_no_list; |
|
} |
|
|
|
/* |
|
* Ok, the hugepage was dissolved. Now these pages are |
|
* Buddy and cannot be re-allocated because they are |
|
* isolated. Fall-through as the check below handles |
|
* Buddy pages. |
|
*/ |
|
} |
|
|
|
/* |
|
* Skip if free. We read page order here without zone lock |
|
* which is generally unsafe, but the race window is small and |
|
* the worst thing that can happen is that we skip some |
|
* potential isolation targets. |
|
*/ |
|
if (PageBuddy(page)) { |
|
unsigned long freepage_order = buddy_order_unsafe(page); |
|
|
|
/* |
|
* Without lock, we cannot be sure that what we got is |
|
* a valid page order. Consider only values in the |
|
* valid order range to prevent low_pfn overflow. |
|
*/ |
|
if (freepage_order > 0 && freepage_order < MAX_ORDER) |
|
low_pfn += (1UL << freepage_order) - 1; |
|
continue; |
|
} |
|
|
|
/* |
|
* Regardless of being on LRU, compound pages such as THP and |
|
* hugetlbfs are not to be compacted unless we are attempting |
|
* an allocation much larger than the huge page size (eg CMA). |
|
* We can potentially save a lot of iterations if we skip them |
|
* at once. The check is racy, but we can consider only valid |
|
* values and the only danger is skipping too much. |
|
*/ |
|
if (PageCompound(page) && !cc->alloc_contig) { |
|
const unsigned int order = compound_order(page); |
|
|
|
if (likely(order < MAX_ORDER)) |
|
low_pfn += (1UL << order) - 1; |
|
goto isolate_fail; |
|
} |
|
|
|
/* |
|
* Check may be lockless but that's ok as we recheck later. |
|
* It's possible to migrate LRU and non-lru movable pages. |
|
* Skip any other type of page |
|
*/ |
|
if (!PageLRU(page)) { |
|
/* |
|
* __PageMovable can return false positive so we need |
|
* to verify it under page_lock. |
|
*/ |
|
if (unlikely(__PageMovable(page)) && |
|
!PageIsolated(page)) { |
|
if (locked) { |
|
unlock_page_lruvec_irqrestore(locked, flags); |
|
locked = NULL; |
|
} |
|
|
|
if (!isolate_movable_page(page, mode)) |
|
goto isolate_success; |
|
} |
|
|
|
goto isolate_fail; |
|
} |
|
|
|
/* |
|
* Be careful not to clear PageLRU until after we're |
|
* sure the page is not being freed elsewhere -- the |
|
* page release code relies on it. |
|
*/ |
|
if (unlikely(!get_page_unless_zero(page))) |
|
goto isolate_fail; |
|
|
|
/* |
|
* Migration will fail if an anonymous page is pinned in memory, |
|
* so avoid taking lru_lock and isolating it unnecessarily in an |
|
* admittedly racy check. |
|
*/ |
|
mapping = page_mapping(page); |
|
if (!mapping && (page_count(page) - 1) > total_mapcount(page)) |
|
goto isolate_fail_put; |
|
|
|
/* |
|
* Only allow to migrate anonymous pages in GFP_NOFS context |
|
* because those do not depend on fs locks. |
|
*/ |
|
if (!(cc->gfp_mask & __GFP_FS) && mapping) |
|
goto isolate_fail_put; |
|
|
|
/* Only take pages on LRU: a check now makes later tests safe */ |
|
if (!PageLRU(page)) |
|
goto isolate_fail_put; |
|
|
|
/* Compaction might skip unevictable pages but CMA takes them */ |
|
if (!(mode & ISOLATE_UNEVICTABLE) && PageUnevictable(page)) |
|
goto isolate_fail_put; |
|
|
|
/* |
|
* To minimise LRU disruption, the caller can indicate with |
|
* ISOLATE_ASYNC_MIGRATE that it only wants to isolate pages |
|
* it will be able to migrate without blocking - clean pages |
|
* for the most part. PageWriteback would require blocking. |
|
*/ |
|
if ((mode & ISOLATE_ASYNC_MIGRATE) && PageWriteback(page)) |
|
goto isolate_fail_put; |
|
|
|
if ((mode & ISOLATE_ASYNC_MIGRATE) && PageDirty(page)) { |
|
bool migrate_dirty; |
|
|
|
/* |
|
* Only pages without mappings or that have a |
|
* ->migrate_folio callback are possible to migrate |
|
* without blocking. However, we can be racing with |
|
* truncation so it's necessary to lock the page |
|
* to stabilise the mapping as truncation holds |
|
* the page lock until after the page is removed |
|
* from the page cache. |
|
*/ |
|
if (!trylock_page(page)) |
|
goto isolate_fail_put; |
|
|
|
mapping = page_mapping(page); |
|
migrate_dirty = !mapping || |
|
mapping->a_ops->migrate_folio; |
|
unlock_page(page); |
|
if (!migrate_dirty) |
|
goto isolate_fail_put; |
|
} |
|
|
|
/* Try isolate the page */ |
|
if (!TestClearPageLRU(page)) |
|
goto isolate_fail_put; |
|
|
|
lruvec = folio_lruvec(page_folio(page)); |
|
|
|
/* If we already hold the lock, we can skip some rechecking */ |
|
if (lruvec != locked) { |
|
if (locked) |
|
unlock_page_lruvec_irqrestore(locked, flags); |
|
|
|
compact_lock_irqsave(&lruvec->lru_lock, &flags, cc); |
|
locked = lruvec; |
|
|
|
lruvec_memcg_debug(lruvec, page_folio(page)); |
|
|
|
/* Try get exclusive access under lock */ |
|
if (!skip_updated) { |
|
skip_updated = true; |
|
if (test_and_set_skip(cc, page, low_pfn)) |
|
goto isolate_abort; |
|
} |
|
|
|
/* |
|
* Page become compound since the non-locked check, |
|
* and it's on LRU. It can only be a THP so the order |
|
* is safe to read and it's 0 for tail pages. |
|
*/ |
|
if (unlikely(PageCompound(page) && !cc->alloc_contig)) { |
|
low_pfn += compound_nr(page) - 1; |
|
SetPageLRU(page); |
|
goto isolate_fail_put; |
|
} |
|
} |
|
|
|
/* The whole page is taken off the LRU; skip the tail pages. */ |
|
if (PageCompound(page)) |
|
low_pfn += compound_nr(page) - 1; |
|
|
|
/* Successfully isolated */ |
|
del_page_from_lru_list(page, lruvec); |
|
mod_node_page_state(page_pgdat(page), |
|
NR_ISOLATED_ANON + page_is_file_lru(page), |
|
thp_nr_pages(page)); |
|
|
|
isolate_success: |
|
list_add(&page->lru, &cc->migratepages); |
|
isolate_success_no_list: |
|
cc->nr_migratepages += compound_nr(page); |
|
nr_isolated += compound_nr(page); |
|
nr_scanned += compound_nr(page) - 1; |
|
|
|
/* |
|
* Avoid isolating too much unless this block is being |
|
* rescanned (e.g. dirty/writeback pages, parallel allocation) |
|
* or a lock is contended. For contention, isolate quickly to |
|
* potentially remove one source of contention. |
|
*/ |
|
if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX && |
|
!cc->rescan && !cc->contended) { |
|
++low_pfn; |
|
break; |
|
} |
|
|
|
continue; |
|
|
|
isolate_fail_put: |
|
/* Avoid potential deadlock in freeing page under lru_lock */ |
|
if (locked) { |
|
unlock_page_lruvec_irqrestore(locked, flags); |
|
locked = NULL; |
|
} |
|
put_page(page); |
|
|
|
isolate_fail: |
|
if (!skip_on_failure && ret != -ENOMEM) |
|
continue; |
|
|
|
/* |
|
* We have isolated some pages, but then failed. Release them |
|
* instead of migrating, as we cannot form the cc->order buddy |
|
* page anyway. |
|
*/ |
|
if (nr_isolated) { |
|
if (locked) { |
|
unlock_page_lruvec_irqrestore(locked, flags); |
|
locked = NULL; |
|
} |
|
putback_movable_pages(&cc->migratepages); |
|
cc->nr_migratepages = 0; |
|
nr_isolated = 0; |
|
} |
|
|
|
if (low_pfn < next_skip_pfn) { |
|
low_pfn = next_skip_pfn - 1; |
|
/* |
|
* The check near the loop beginning would have updated |
|
* next_skip_pfn too, but this is a bit simpler. |
|
*/ |
|
next_skip_pfn += 1UL << cc->order; |
|
} |
|
|
|
if (ret == -ENOMEM) |
|
break; |
|
} |
|
|
|
/* |
|
* The PageBuddy() check could have potentially brought us outside |
|
* the range to be scanned. |
|
*/ |
|
if (unlikely(low_pfn > end_pfn)) |
|
low_pfn = end_pfn; |
|
|
|
page = NULL; |
|
|
|
isolate_abort: |
|
if (locked) |
|
unlock_page_lruvec_irqrestore(locked, flags); |
|
if (page) { |
|
SetPageLRU(page); |
|
put_page(page); |
|
} |
|
|
|
/* |
|
* Updated the cached scanner pfn once the pageblock has been scanned |
|
* Pages will either be migrated in which case there is no point |
|
* scanning in the near future or migration failed in which case the |
|
* failure reason may persist. The block is marked for skipping if |
|
* there were no pages isolated in the block or if the block is |
|
* rescanned twice in a row. |
|
*/ |
|
if (low_pfn == end_pfn && (!nr_isolated || cc->rescan)) { |
|
if (valid_page && !skip_updated) |
|
set_pageblock_skip(valid_page); |
|
update_cached_migrate(cc, low_pfn); |
|
} |
|
|
|
trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn, |
|
nr_scanned, nr_isolated); |
|
|
|
fatal_pending: |
|
cc->total_migrate_scanned += nr_scanned; |
|
if (nr_isolated) |
|
count_compact_events(COMPACTISOLATED, nr_isolated); |
|
|
|
cc->migrate_pfn = low_pfn; |
|
|
|
return ret; |
|
} |
|
|
|
/** |
|
* isolate_migratepages_range() - isolate migrate-able pages in a PFN range |
|
* @cc: Compaction control structure. |
|
* @start_pfn: The first PFN to start isolating. |
|
* @end_pfn: The one-past-last PFN. |
|
* |
|
* Returns -EAGAIN when contented, -EINTR in case of a signal pending, -ENOMEM |
|
* in case we could not allocate a page, or 0. |
|
*/ |
|
int |
|
isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, |
|
unsigned long end_pfn) |
|
{ |
|
unsigned long pfn, block_start_pfn, block_end_pfn; |
|
int ret = 0; |
|
|
|
/* Scan block by block. First and last block may be incomplete */ |
|
pfn = start_pfn; |
|
block_start_pfn = pageblock_start_pfn(pfn); |
|
if (block_start_pfn < cc->zone->zone_start_pfn) |
|
block_start_pfn = cc->zone->zone_start_pfn; |
|
block_end_pfn = pageblock_end_pfn(pfn); |
|
|
|
for (; pfn < end_pfn; pfn = block_end_pfn, |
|
block_start_pfn = block_end_pfn, |
|
block_end_pfn += pageblock_nr_pages) { |
|
|
|
block_end_pfn = min(block_end_pfn, end_pfn); |
|
|
|
if (!pageblock_pfn_to_page(block_start_pfn, |
|
block_end_pfn, cc->zone)) |
|
continue; |
|
|
|
ret = isolate_migratepages_block(cc, pfn, block_end_pfn, |
|
ISOLATE_UNEVICTABLE); |
|
|
|
if (ret) |
|
break; |
|
|
|
if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX) |
|
break; |
|
} |
|
|
|
return ret; |
|
} |
|
|
|
#endif /* CONFIG_COMPACTION || CONFIG_CMA */ |
|
#ifdef CONFIG_COMPACTION |
|
|
|
static bool suitable_migration_source(struct compact_control *cc, |
|
struct page *page) |
|
{ |
|
int block_mt; |
|
|
|
if (pageblock_skip_persistent(page)) |
|
return false; |
|
|
|
if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction) |
|
return true; |
|
|
|
block_mt = get_pageblock_migratetype(page); |
|
|
|
if (cc->migratetype == MIGRATE_MOVABLE) |
|
return is_migrate_movable(block_mt); |
|
else |
|
return block_mt == cc->migratetype; |
|
} |
|
|
|
/* Returns true if the page is within a block suitable for migration to */ |
|
static bool suitable_migration_target(struct compact_control *cc, |
|
struct page *page) |
|
{ |
|
/* If the page is a large free page, then disallow migration */ |
|
if (PageBuddy(page)) { |
|
/* |
|
* We are checking page_order without zone->lock taken. But |
|
* the only small danger is that we skip a potentially suitable |
|
* pageblock, so it's not worth to check order for valid range. |
|
*/ |
|
if (buddy_order_unsafe(page) >= pageblock_order) |
|
return false; |
|
} |
|
|
|
if (cc->ignore_block_suitable) |
|
return true; |
|
|
|
/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ |
|
if (is_migrate_movable(get_pageblock_migratetype(page))) |
|
return true; |
|
|
|
/* Otherwise skip the block */ |
|
return false; |
|
} |
|
|
|
static inline unsigned int |
|
freelist_scan_limit(struct compact_control *cc) |
|
{ |
|
unsigned short shift = BITS_PER_LONG - 1; |
|
|
|
return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1; |
|
} |
|
|
|
/* |
|
* Test whether the free scanner has reached the same or lower pageblock than |
|
* the migration scanner, and compaction should thus terminate. |
|
*/ |
|
static inline bool compact_scanners_met(struct compact_control *cc) |
|
{ |
|
return (cc->free_pfn >> pageblock_order) |
|
<= (cc->migrate_pfn >> pageblock_order); |
|
} |
|
|
|
/* |
|
* Used when scanning for a suitable migration target which scans freelists |
|
* in reverse. Reorders the list such as the unscanned pages are scanned |
|
* first on the next iteration of the free scanner |
|
*/ |
|
static void |
|
move_freelist_head(struct list_head *freelist, struct page *freepage) |
|
{ |
|
LIST_HEAD(sublist); |
|
|
|
if (!list_is_last(freelist, &freepage->lru)) { |
|
list_cut_before(&sublist, freelist, &freepage->lru); |
|
list_splice_tail(&sublist, freelist); |
|
} |
|
} |
|
|
|
/* |
|
* Similar to move_freelist_head except used by the migration scanner |
|
* when scanning forward. It's possible for these list operations to |
|
* move against each other if they search the free list exactly in |
|
* lockstep. |
|
*/ |
|
static void |
|
move_freelist_tail(struct list_head *freelist, struct page *freepage) |
|
{ |
|
LIST_HEAD(sublist); |
|
|
|
if (!list_is_first(freelist, &freepage->lru)) { |
|
list_cut_position(&sublist, freelist, &freepage->lru); |
|
list_splice_tail(&sublist, freelist); |
|
} |
|
} |
|
|
|
static void |
|
fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long nr_isolated) |
|
{ |
|
unsigned long start_pfn, end_pfn; |
|
struct page *page; |
|
|
|
/* Do not search around if there are enough pages already */ |
|
if (cc->nr_freepages >= cc->nr_migratepages) |
|
return; |
|
|
|
/* Minimise scanning during async compaction */ |
|
if (cc->direct_compaction && cc->mode == MIGRATE_ASYNC) |
|
return; |
|
|
|
/* Pageblock boundaries */ |
|
start_pfn = max(pageblock_start_pfn(pfn), cc->zone->zone_start_pfn); |
|
end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone)); |
|
|
|
page = pageblock_pfn_to_page(start_pfn, end_pfn, cc->zone); |
|
if (!page) |
|
return; |
|
|
|
/* Scan before */ |
|
if (start_pfn != pfn) { |
|
isolate_freepages_block(cc, &start_pfn, pfn, &cc->freepages, 1, false); |
|
if (cc->nr_freepages >= cc->nr_migratepages) |
|
return; |
|
} |
|
|
|
/* Scan after */ |
|
start_pfn = pfn + nr_isolated; |
|
if (start_pfn < end_pfn) |
|
isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false); |
|
|
|
/* Skip this pageblock in the future as it's full or nearly full */ |
|
if (cc->nr_freepages < cc->nr_migratepages) |
|
set_pageblock_skip(page); |
|
} |
|
|
|
/* Search orders in round-robin fashion */ |
|
static int next_search_order(struct compact_control *cc, int order) |
|
{ |
|
order--; |
|
if (order < 0) |
|
order = cc->order - 1; |
|
|
|
/* Search wrapped around? */ |
|
if (order == cc->search_order) { |
|
cc->search_order--; |
|
if (cc->search_order < 0) |
|
cc->search_order = cc->order - 1; |
|
return -1; |
|
} |
|
|
|
return order; |
|
} |
|
|
|
static unsigned long |
|
fast_isolate_freepages(struct compact_control *cc) |
|
{ |
|
unsigned int limit = max(1U, freelist_scan_limit(cc) >> 1); |
|
unsigned int nr_scanned = 0; |
|
unsigned long low_pfn, min_pfn, highest = 0; |
|
unsigned long nr_isolated = 0; |
|
unsigned long distance; |
|
struct page *page = NULL; |
|
bool scan_start = false; |
|
int order; |
|
|
|
/* Full compaction passes in a negative order */ |
|
if (cc->order <= 0) |
|
return cc->free_pfn; |
|
|
|
/* |
|
* If starting the scan, use a deeper search and use the highest |
|
* PFN found if a suitable one is not found. |
|
*/ |
|
if (cc->free_pfn >= cc->zone->compact_init_free_pfn) { |
|
limit = pageblock_nr_pages >> 1; |
|
scan_start = true; |
|
} |
|
|
|
/* |
|
* Preferred point is in the top quarter of the scan space but take |
|
* a pfn from the top half if the search is problematic. |
|
*/ |
|
distance = (cc->free_pfn - cc->migrate_pfn); |
|
low_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 2)); |
|
min_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 1)); |
|
|
|
if (WARN_ON_ONCE(min_pfn > low_pfn)) |
|
low_pfn = min_pfn; |
|
|
|
/* |
|
* Search starts from the last successful isolation order or the next |
|
* order to search after a previous failure |
|
*/ |
|
cc->search_order = min_t(unsigned int, cc->order - 1, cc->search_order); |
|
|
|
for (order = cc->search_order; |
|
!page && order >= 0; |
|
order = next_search_order(cc, order)) { |
|
struct free_area *area = &cc->zone->free_area[order]; |
|
struct list_head *freelist; |
|
struct page *freepage; |
|
unsigned long flags; |
|
unsigned int order_scanned = 0; |
|
unsigned long high_pfn = 0; |
|
|
|
if (!area->nr_free) |
|
continue; |
|
|
|
spin_lock_irqsave(&cc->zone->lock, flags); |
|
freelist = &area->free_list[MIGRATE_MOVABLE]; |
|
list_for_each_entry_reverse(freepage, freelist, lru) { |
|
unsigned long pfn; |
|
|
|
order_scanned++; |
|
nr_scanned++; |
|
pfn = page_to_pfn(freepage); |
|
|
|
if (pfn >= highest) |
|
highest = max(pageblock_start_pfn(pfn), |
|
cc->zone->zone_start_pfn); |
|
|
|
if (pfn >= low_pfn) { |
|
cc->fast_search_fail = 0; |
|
cc->search_order = order; |
|
page = freepage; |
|
break; |
|
} |
|
|
|
if (pfn >= min_pfn && pfn > high_pfn) { |
|
high_pfn = pfn; |
|
|
|
/* Shorten the scan if a candidate is found */ |
|
limit >>= 1; |
|
} |
|
|
|
if (order_scanned >= limit) |
|
break; |
|
} |
|
|
|
/* Use a minimum pfn if a preferred one was not found */ |
|
if (!page && high_pfn) { |
|
page = pfn_to_page(high_pfn); |
|
|
|
/* Update freepage for the list reorder below */ |
|
freepage = page; |
|
} |
|
|
|
/* Reorder to so a future search skips recent pages */ |
|
move_freelist_head(freelist, freepage); |
|
|
|
/* Isolate the page if available */ |
|
if (page) { |
|
if (__isolate_free_page(page, order)) { |
|
set_page_private(page, order); |
|
nr_isolated = 1 << order; |
|
nr_scanned += nr_isolated - 1; |
|
cc->nr_freepages += nr_isolated; |
|
list_add_tail(&page->lru, &cc->freepages); |
|
count_compact_events(COMPACTISOLATED, nr_isolated); |
|
} else { |
|
/* If isolation fails, abort the search */ |
|
order = cc->search_order + 1; |
|
page = NULL; |
|
} |
|
} |
|
|
|
spin_unlock_irqrestore(&cc->zone->lock, flags); |
|
|
|
/* |
|
* Smaller scan on next order so the total scan is related |
|
* to freelist_scan_limit. |
|
*/ |
|
if (order_scanned >= limit) |
|
limit = max(1U, limit >> 1); |
|
} |
|
|
|
if (!page) { |
|
cc->fast_search_fail++; |
|
if (scan_start) { |
|
/* |
|
* Use the highest PFN found above min. If one was |
|
* not found, be pessimistic for direct compaction |
|
* and use the min mark. |
|
*/ |
|
if (highest >= min_pfn) { |
|
page = pfn_to_page(highest); |
|
cc->free_pfn = highest; |
|
} else { |
|
if (cc->direct_compaction && pfn_valid(min_pfn)) { |
|
page = pageblock_pfn_to_page(min_pfn, |
|
min(pageblock_end_pfn(min_pfn), |
|
zone_end_pfn(cc->zone)), |
|
cc->zone); |
|
cc->free_pfn = min_pfn; |
|
} |
|
} |
|
} |
|
} |
|
|
|
if (highest && highest >= cc->zone->compact_cached_free_pfn) { |
|
highest -= pageblock_nr_pages; |
|
cc->zone->compact_cached_free_pfn = highest; |
|
} |
|
|
|
cc->total_free_scanned += nr_scanned; |
|
if (!page) |
|
return cc->free_pfn; |
|
|
|
low_pfn = page_to_pfn(page); |
|
fast_isolate_around(cc, low_pfn, nr_isolated); |
|
return low_pfn; |
|
} |
|
|
|
/* |
|
* Based on information in the current compact_control, find blocks |
|
* suitable for isolating free pages from and then isolate them. |
|
*/ |
|
static void isolate_freepages(struct compact_control *cc) |
|
{ |
|
struct zone *zone = cc->zone; |
|
struct page *page; |
|
unsigned long block_start_pfn; /* start of current pageblock */ |
|
unsigned long isolate_start_pfn; /* exact pfn we start at */ |
|
unsigned long block_end_pfn; /* end of current pageblock */ |
|
unsigned long low_pfn; /* lowest pfn scanner is able to scan */ |
|
struct list_head *freelist = &cc->freepages; |
|
unsigned int stride; |
|
|
|
/* Try a small search of the free lists for a candidate */ |
|
fast_isolate_freepages(cc); |
|
if (cc->nr_freepages) |
|
goto splitmap; |
|
|
|
/* |
|
* Initialise the free scanner. The starting point is where we last |
|
* successfully isolated from, zone-cached value, or the end of the |
|
* zone when isolating for the first time. For looping we also need |
|
* this pfn aligned down to the pageblock boundary, because we do |
|
* block_start_pfn -= pageblock_nr_pages in the for loop. |
|
* For ending point, take care when isolating in last pageblock of a |
|
* zone which ends in the middle of a pageblock. |
|
* The low boundary is the end of the pageblock the migration scanner |
|
* is using. |
|
*/ |
|
isolate_start_pfn = cc->free_pfn; |
|
block_start_pfn = pageblock_start_pfn(isolate_start_pfn); |
|
block_end_pfn = min(block_start_pfn + pageblock_nr_pages, |
|
zone_end_pfn(zone)); |
|
low_pfn = pageblock_end_pfn(cc->migrate_pfn); |
|
stride = cc->mode == MIGRATE_ASYNC ? COMPACT_CLUSTER_MAX : 1; |
|
|
|
/* |
|
* Isolate free pages until enough are available to migrate the |
|
* pages on cc->migratepages. We stop searching if the migrate |
|
* and free page scanners meet or enough free pages are isolated. |
|
*/ |
|
for (; block_start_pfn >= low_pfn; |
|
block_end_pfn = block_start_pfn, |
|
block_start_pfn -= pageblock_nr_pages, |
|
isolate_start_pfn = block_start_pfn) { |
|
unsigned long nr_isolated; |
|
|
|
/* |
|
* This can iterate a massively long zone without finding any |
|
* suitable migration targets, so periodically check resched. |
|
*/ |
|
if (!(block_start_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages))) |
|
cond_resched(); |
|
|
|
page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, |
|
zone); |
|
if (!page) |
|
continue; |
|
|
|
/* Check the block is suitable for migration */ |
|
if (!suitable_migration_target(cc, page)) |
|
continue; |
|
|
|
/* If isolation recently failed, do not retry */ |
|
if (!isolation_suitable(cc, page)) |
|
continue; |
|
|
|
/* Found a block suitable for isolating free pages from. */ |
|
nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn, |
|
block_end_pfn, freelist, stride, false); |
|
|
|
/* Update the skip hint if the full pageblock was scanned */ |
|
if (isolate_start_pfn == block_end_pfn) |
|
update_pageblock_skip(cc, page, block_start_pfn); |
|
|
|
/* Are enough freepages isolated? */ |
|
if (cc->nr_freepages >= cc->nr_migratepages) { |
|
if (isolate_start_pfn >= block_end_pfn) { |
|
/* |
|
* Restart at previous pageblock if more |
|
* freepages can be isolated next time. |
|
*/ |
|
isolate_start_pfn = |
|
block_start_pfn - pageblock_nr_pages; |
|
} |
|
break; |
|
} else if (isolate_start_pfn < block_end_pfn) { |
|
/* |
|
* If isolation failed early, do not continue |
|
* needlessly. |
|
*/ |
|
break; |
|
} |
|
|
|
/* Adjust stride depending on isolation */ |
|
if (nr_isolated) { |
|
stride = 1; |
|
continue; |
|
} |
|
stride = min_t(unsigned int, COMPACT_CLUSTER_MAX, stride << 1); |
|
} |
|
|
|
/* |
|
* Record where the free scanner will restart next time. Either we |
|
* broke from the loop and set isolate_start_pfn based on the last |
|
* call to isolate_freepages_block(), or we met the migration scanner |
|
* and the loop terminated due to isolate_start_pfn < low_pfn |
|
*/ |
|
cc->free_pfn = isolate_start_pfn; |
|
|
|
splitmap: |
|
/* __isolate_free_page() does not map the pages */ |
|
split_map_pages(freelist); |
|
} |
|
|
|
/* |
|
* This is a migrate-callback that "allocates" freepages by taking pages |
|
* from the isolated freelists in the block we are migrating to. |
|
*/ |
|
static struct page *compaction_alloc(struct page *migratepage, |
|
unsigned long data) |
|
{ |
|
struct compact_control *cc = (struct compact_control *)data; |
|
struct page *freepage; |
|
|
|
if (list_empty(&cc->freepages)) { |
|
isolate_freepages(cc); |
|
|
|
if (list_empty(&cc->freepages)) |
|
return NULL; |
|
} |
|
|
|
freepage = list_entry(cc->freepages.next, struct page, lru); |
|
list_del(&freepage->lru); |
|
cc->nr_freepages--; |
|
|
|
return freepage; |
|
} |
|
|
|
/* |
|
* This is a migrate-callback that "frees" freepages back to the isolated |
|
* freelist. All pages on the freelist are from the same zone, so there is no |
|
* special handling needed for NUMA. |
|
*/ |
|
static void compaction_free(struct page *page, unsigned long data) |
|
{ |
|
struct compact_control *cc = (struct compact_control *)data; |
|
|
|
list_add(&page->lru, &cc->freepages); |
|
cc->nr_freepages++; |
|
} |
|
|
|
/* possible outcome of isolate_migratepages */ |
|
typedef enum { |
|
ISOLATE_ABORT, /* Abort compaction now */ |
|
ISOLATE_NONE, /* No pages isolated, continue scanning */ |
|
ISOLATE_SUCCESS, /* Pages isolated, migrate */ |
|
} isolate_migrate_t; |
|
|
|
/* |
|
* Allow userspace to control policy on scanning the unevictable LRU for |
|
* compactable pages. |
|
*/ |
|
int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNEVICTABLE_DEFAULT; |
|
|
|
static inline void |
|
update_fast_start_pfn(struct compact_control *cc, unsigned long pfn) |
|
{ |
|
if (cc->fast_start_pfn == ULONG_MAX) |
|
return; |
|
|
|
if (!cc->fast_start_pfn) |
|
cc->fast_start_pfn = pfn; |
|
|
|
cc->fast_start_pfn = min(cc->fast_start_pfn, pfn); |
|
} |
|
|
|
static inline unsigned long |
|
reinit_migrate_pfn(struct compact_control *cc) |
|
{ |
|
if (!cc->fast_start_pfn || cc->fast_start_pfn == ULONG_MAX) |
|
return cc->migrate_pfn; |
|
|
|
cc->migrate_pfn = cc->fast_start_pfn; |
|
cc->fast_start_pfn = ULONG_MAX; |
|
|
|
return cc->migrate_pfn; |
|
} |
|
|
|
/* |
|
* Briefly search the free lists for a migration source that already has |
|
* some free pages to reduce the number of pages that need migration |
|
* before a pageblock is free. |
|
*/ |
|
static unsigned long fast_find_migrateblock(struct compact_control *cc) |
|
{ |
|
unsigned int limit = freelist_scan_limit(cc); |
|
unsigned int nr_scanned = 0; |
|
unsigned long distance; |
|
unsigned long pfn = cc->migrate_pfn; |
|
unsigned long high_pfn; |
|
int order; |
|
bool found_block = false; |
|
|
|
/* Skip hints are relied on to avoid repeats on the fast search */ |
|
if (cc->ignore_skip_hint) |
|
return pfn; |
|
|
|
/* |
|
* If the migrate_pfn is not at the start of a zone or the start |
|
* of a pageblock then assume this is a continuation of a previous |
|
* scan restarted due to COMPACT_CLUSTER_MAX. |
|
*/ |
|
if (pfn != cc->zone->zone_start_pfn && pfn != pageblock_start_pfn(pfn)) |
|
return pfn; |
|
|
|
/* |
|
* For smaller orders, just linearly scan as the number of pages |
|
* to migrate should be relatively small and does not necessarily |
|
* justify freeing up a large block for a small allocation. |
|
*/ |
|
if (cc->order <= PAGE_ALLOC_COSTLY_ORDER) |
|
return pfn; |
|
|
|
/* |
|
* Only allow kcompactd and direct requests for movable pages to |
|
* quickly clear out a MOVABLE pageblock for allocation. This |
|
* reduces the risk that a large movable pageblock is freed for |
|
* an unmovable/reclaimable small allocation. |
|
*/ |
|
if (cc->direct_compaction && cc->migratetype != MIGRATE_MOVABLE) |
|
return pfn; |
|
|
|
/* |
|
* When starting the migration scanner, pick any pageblock within the |
|
* first half of the search space. Otherwise try and pick a pageblock |
|
* within the first eighth to reduce the chances that a migration |
|
* target later becomes a source. |
|
*/ |
|
distance = (cc->free_pfn - cc->migrate_pfn) >> 1; |
|
if (cc->migrate_pfn != cc->zone->zone_start_pfn) |
|
distance >>= 2; |
|
high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance); |
|
|
|
for (order = cc->order - 1; |
|
order >= PAGE_ALLOC_COSTLY_ORDER && !found_block && nr_scanned < limit; |
|
order--) { |
|
struct free_area *area = &cc->zone->free_area[order]; |
|
struct list_head *freelist; |
|
unsigned long flags; |
|
struct page *freepage; |
|
|
|
if (!area->nr_free) |
|
continue; |
|
|
|
spin_lock_irqsave(&cc->zone->lock, flags); |
|
freelist = &area->free_list[MIGRATE_MOVABLE]; |
|
list_for_each_entry(freepage, freelist, lru) { |
|
unsigned long free_pfn; |
|
|
|
if (nr_scanned++ >= limit) { |
|
move_freelist_tail(freelist, freepage); |
|
break; |
|
} |
|
|
|
free_pfn = page_to_pfn(freepage); |
|
if (free_pfn < high_pfn) { |
|
/* |
|
* Avoid if skipped recently. Ideally it would |
|
* move to the tail but even safe iteration of |
|
* the list assumes an entry is deleted, not |
|
* reordered. |
|
*/ |
|
if (get_pageblock_skip(freepage)) |
|
continue; |
|
|
|
/* Reorder to so a future search skips recent pages */ |
|
move_freelist_tail(freelist, freepage); |
|
|
|
update_fast_start_pfn(cc, free_pfn); |
|
pfn = pageblock_start_pfn(free_pfn); |
|
if (pfn < cc->zone->zone_start_pfn) |
|
pfn = cc->zone->zone_start_pfn; |
|
cc->fast_search_fail = 0; |
|
found_block = true; |
|
break; |
|
} |
|
} |
|
spin_unlock_irqrestore(&cc->zone->lock, flags); |
|
} |
|
|
|
cc->total_migrate_scanned += nr_scanned; |
|
|
|
/* |
|
* If fast scanning failed then use a cached entry for a page block |
|
* that had free pages as the basis for starting a linear scan. |
|
*/ |
|
if (!found_block) { |
|
cc->fast_search_fail++; |
|
pfn = reinit_migrate_pfn(cc); |
|
} |
|
return pfn; |
|
} |
|
|
|
/* |
|
* Isolate all pages that can be migrated from the first suitable block, |
|
* starting at the block pointed to by the migrate scanner pfn within |
|
* compact_control. |
|
*/ |
|
static isolate_migrate_t isolate_migratepages(struct compact_control *cc) |
|
{ |
|
unsigned long block_start_pfn; |
|
unsigned long block_end_pfn; |
|
unsigned long low_pfn; |
|
struct page *page; |
|
const isolate_mode_t isolate_mode = |
|
(sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | |
|
(cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); |
|
bool fast_find_block; |
|
|
|
/* |
|
* Start at where we last stopped, or beginning of the zone as |
|
* initialized by compact_zone(). The first failure will use |
|
* the lowest PFN as the starting point for linear scanning. |
|
*/ |
|
low_pfn = fast_find_migrateblock(cc); |
|
block_start_pfn = pageblock_start_pfn(low_pfn); |
|
if (block_start_pfn < cc->zone->zone_start_pfn) |
|
block_start_pfn = cc->zone->zone_start_pfn; |
|
|
|
/* |
|
* fast_find_migrateblock marks a pageblock skipped so to avoid |
|
* the isolation_suitable check below, check whether the fast |
|
* search was successful. |
|
*/ |
|
fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; |
|
|
|
/* Only scan within a pageblock boundary */ |
|
block_end_pfn = pageblock_end_pfn(low_pfn); |
|
|
|
/* |
|
* Iterate over whole pageblocks until we find the first suitable. |
|
* Do not cross the free scanner. |
|
*/ |
|
for (; block_end_pfn <= cc->free_pfn; |
|
fast_find_block = false, |
|
cc->migrate_pfn = low_pfn = block_end_pfn, |
|
block_start_pfn = block_end_pfn, |
|
block_end_pfn += pageblock_nr_pages) { |
|
|
|
/* |
|
* This can potentially iterate a massively long zone with |
|
* many pageblocks unsuitable, so periodically check if we |
|
* need to schedule. |
|
*/ |
|
if (!(low_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages))) |
|
cond_resched(); |
|
|
|
page = pageblock_pfn_to_page(block_start_pfn, |
|
block_end_pfn, cc->zone); |
|
if (!page) |
|
continue; |
|
|
|
/* |
|
* If isolation recently failed, do not retry. Only check the |
|
* pageblock once. COMPACT_CLUSTER_MAX causes a pageblock |
|
* to be visited multiple times. Assume skip was checked |
|
* before making it "skip" so other compaction instances do |
|
* not scan the same block. |
|
*/ |
|
if (pageblock_aligned(low_pfn) && |
|
!fast_find_block && !isolation_suitable(cc, page)) |
|
continue; |
|
|
|
/* |
|
* For async direct compaction, only scan the pageblocks of the |
|
* same migratetype without huge pages. Async direct compaction |
|
* is optimistic to see if the minimum amount of work satisfies |
|
* the allocation. The cached PFN is updated as it's possible |
|
* that all remaining blocks between source and target are |
|
* unsuitable and the compaction scanners fail to meet. |
|
*/ |
|
if (!suitable_migration_source(cc, page)) { |
|
update_cached_migrate(cc, block_end_pfn); |
|
continue; |
|
} |
|
|
|
/* Perform the isolation */ |
|
if (isolate_migratepages_block(cc, low_pfn, block_end_pfn, |
|
isolate_mode)) |
|
return ISOLATE_ABORT; |
|
|
|
/* |
|
* Either we isolated something and proceed with migration. Or |
|
* we failed and compact_zone should decide if we should |
|
* continue or not. |
|
*/ |
|
break; |
|
} |
|
|
|
return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE; |
|
} |
|
|
|
/* |
|
* order == -1 is expected when compacting via |
|
* /proc/sys/vm/compact_memory |
|
*/ |
|
static inline bool is_via_compact_memory(int order) |
|
{ |
|
return order == -1; |
|
} |
|
|
|
/* |
|
* Determine whether kswapd is (or recently was!) running on this node. |
|
* |
|
* pgdat_kswapd_lock() pins pgdat->kswapd, so a concurrent kswapd_stop() can't |
|
* zero it. |
|
*/ |
|
static bool kswapd_is_running(pg_data_t *pgdat) |
|
{ |
|
bool running; |
|
|
|
pgdat_kswapd_lock(pgdat); |
|
running = pgdat->kswapd && task_is_running(pgdat->kswapd); |
|
pgdat_kswapd_unlock(pgdat); |
|
|
|
return running; |
|
} |
|
|
|
/* |
|
* A zone's fragmentation score is the external fragmentation wrt to the |
|
* COMPACTION_HPAGE_ORDER. It returns a value in the range [0, 100]. |
|
*/ |
|
static unsigned int fragmentation_score_zone(struct zone *zone) |
|
{ |
|
return extfrag_for_order(zone, COMPACTION_HPAGE_ORDER); |
|
} |
|
|
|
/* |
|
* A weighted zone's fragmentation score is the external fragmentation |
|
* wrt to the COMPACTION_HPAGE_ORDER scaled by the zone's size. It |
|
* returns a value in the range [0, 100]. |
|
* |
|
* The scaling factor ensures that proactive compaction focuses on larger |
|
* zones like ZONE_NORMAL, rather than smaller, specialized zones like |
|
* ZONE_DMA32. For smaller zones, the score value remains close to zero, |
|
* and thus never exceeds the high threshold for proactive compaction. |
|
*/ |
|
static unsigned int fragmentation_score_zone_weighted(struct zone *zone) |
|
{ |
|
unsigned long score; |
|
|
|
score = zone->present_pages * fragmentation_score_zone(zone); |
|
return div64_ul(score, zone->zone_pgdat->node_present_pages + 1); |
|
} |
|
|
|
/* |
|
* The per-node proactive (background) compaction process is started by its |
|
* corresponding kcompactd thread when the node's fragmentation score |
|
* exceeds the high threshold. The compaction process remains active till |
|
* the node's score falls below the low threshold, or one of the back-off |
|
* conditions is met. |
|
*/ |
|
static unsigned int fragmentation_score_node(pg_data_t *pgdat) |
|
{ |
|
unsigned int score = 0; |
|
int zoneid; |
|
|
|
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
|
struct zone *zone; |
|
|
|
zone = &pgdat->node_zones[zoneid]; |
|
score += fragmentation_score_zone_weighted(zone); |
|
} |
|
|
|
return score; |
|
} |
|
|
|
static unsigned int fragmentation_score_wmark(pg_data_t *pgdat, bool low) |
|
{ |
|
unsigned int wmark_low; |
|
|
|
/* |
|
* Cap the low watermark to avoid excessive compaction |
|
* activity in case a user sets the proactiveness tunable |
|
* close to 100 (maximum). |
|
*/ |
|
wmark_low = max(100U - sysctl_compaction_proactiveness, 5U); |
|
return low ? wmark_low : min(wmark_low + 10, 100U); |
|
} |
|
|
|
static bool should_proactive_compact_node(pg_data_t *pgdat) |
|
{ |
|
int wmark_high; |
|
|
|
if (!sysctl_compaction_proactiveness || kswapd_is_running(pgdat)) |
|
return false; |
|
|
|
wmark_high = fragmentation_score_wmark(pgdat, false); |
|
return fragmentation_score_node(pgdat) > wmark_high; |
|
} |
|
|
|
static enum compact_result __compact_finished(struct compact_control *cc) |
|
{ |
|
unsigned int order; |
|
const int migratetype = cc->migratetype; |
|
int ret; |
|
|
|
/* Compaction run completes if the migrate and free scanner meet */ |
|
if (compact_scanners_met(cc)) { |
|
/* Let the next compaction start anew. */ |
|
reset_cached_positions(cc->zone); |
|
|
|
/* |
|
* Mark that the PG_migrate_skip information should be cleared |
|
* by kswapd when it goes to sleep. kcompactd does not set the |
|
* flag itself as the decision to be clear should be directly |
|
* based on an allocation request. |
|
*/ |
|
if (cc->direct_compaction) |
|
cc->zone->compact_blockskip_flush = true; |
|
|
|
if (cc->whole_zone) |
|
return COMPACT_COMPLETE; |
|
else |
|
return COMPACT_PARTIAL_SKIPPED; |
|
} |
|
|
|
if (cc->proactive_compaction) { |
|
int score, wmark_low; |
|
pg_data_t *pgdat; |
|
|
|
pgdat = cc->zone->zone_pgdat; |
|
if (kswapd_is_running(pgdat)) |
|
return COMPACT_PARTIAL_SKIPPED; |
|
|
|
score = fragmentation_score_zone(cc->zone); |
|
wmark_low = fragmentation_score_wmark(pgdat, true); |
|
|
|
if (score > wmark_low) |
|
ret = COMPACT_CONTINUE; |
|
else |
|
ret = COMPACT_SUCCESS; |
|
|
|
goto out; |
|
} |
|
|
|
if (is_via_compact_memory(cc->order)) |
|
return COMPACT_CONTINUE; |
|
|
|
/* |
|
* Always finish scanning a pageblock to reduce the possibility of |
|
* fallbacks in the future. This is particularly important when |
|
* migration source is unmovable/reclaimable but it's not worth |
|
* special casing. |
|
*/ |
|
if (!pageblock_aligned(cc->migrate_pfn)) |
|
return COMPACT_CONTINUE; |
|
|
|
/* Direct compactor: Is a suitable page free? */ |
|
ret = COMPACT_NO_SUITABLE_PAGE; |
|
for (order = cc->order; order < MAX_ORDER; order++) { |
|
struct free_area *area = &cc->zone->free_area[order]; |
|
bool can_steal; |
|
|
|
/* Job done if page is free of the right migratetype */ |
|
if (!free_area_empty(area, migratetype)) |
|
return COMPACT_SUCCESS; |
|
|
|
#ifdef CONFIG_CMA |
|
/* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */ |
|
if (migratetype == MIGRATE_MOVABLE && |
|
!free_area_empty(area, MIGRATE_CMA)) |
|
return COMPACT_SUCCESS; |
|
#endif |
|
/* |
|
* Job done if allocation would steal freepages from |
|
* other migratetype buddy lists. |
|
*/ |
|
if (find_suitable_fallback(area, order, migratetype, |
|
true, &can_steal) != -1) |
|
/* |
|
* Movable pages are OK in any pageblock. If we are |
|
* stealing for a non-movable allocation, make sure |
|
* we finish compacting the current pageblock first |
|
* (which is assured by the above migrate_pfn align |
|
* check) so it is as free as possible and we won't |
|
* have to steal another one soon. |
|
*/ |
|
return COMPACT_SUCCESS; |
|
} |
|
|
|
out: |
|
if (cc->contended || fatal_signal_pending(current)) |
|
ret = COMPACT_CONTENDED; |
|
|
|
return ret; |
|
} |
|
|
|
static enum compact_result compact_finished(struct compact_control *cc) |
|
{ |
|
int ret; |
|
|
|
ret = __compact_finished(cc); |
|
trace_mm_compaction_finished(cc->zone, cc->order, ret); |
|
if (ret == COMPACT_NO_SUITABLE_PAGE) |
|
ret = COMPACT_CONTINUE; |
|
|
|
return ret; |
|
} |
|
|
|
static enum compact_result __compaction_suitable(struct zone *zone, int order, |
|
unsigned int alloc_flags, |
|
int highest_zoneidx, |
|
unsigned long wmark_target) |
|
{ |
|
unsigned long watermark; |
|
|
|
if (is_via_compact_memory(order)) |
|
return COMPACT_CONTINUE; |
|
|
|
watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK); |
|
/* |
|
* If watermarks for high-order allocation are already met, there |
|
* should be no need for compaction at all. |
|
*/ |
|
if (zone_watermark_ok(zone, order, watermark, highest_zoneidx, |
|
alloc_flags)) |
|
return COMPACT_SUCCESS; |
|
|
|
/* |
|
* Watermarks for order-0 must be met for compaction to be able to |
|
* isolate free pages for migration targets. This means that the |
|
* watermark and alloc_flags have to match, or be more pessimistic than |
|
* the check in __isolate_free_page(). We don't use the direct |
|
* compactor's alloc_flags, as they are not relevant for freepage |
|
* isolation. We however do use the direct compactor's highest_zoneidx |
|
* to skip over zones where lowmem reserves would prevent allocation |
|
* even if compaction succeeds. |
|
* For costly orders, we require low watermark instead of min for |
|
* compaction to proceed to increase its chances. |
|
* ALLOC_CMA is used, as pages in CMA pageblocks are considered |
|
* suitable migration targets |
|
*/ |
|
watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ? |
|
low_wmark_pages(zone) : min_wmark_pages(zone); |
|
watermark += compact_gap(order); |
|
if (!__zone_watermark_ok(zone, 0, watermark, highest_zoneidx, |
|
ALLOC_CMA, wmark_target)) |
|
return COMPACT_SKIPPED; |
|
|
|
return COMPACT_CONTINUE; |
|
} |
|
|
|
/* |
|
* compaction_suitable: Is this suitable to run compaction on this zone now? |
|
* Returns |
|
* COMPACT_SKIPPED - If there are too few free pages for compaction |
|
* COMPACT_SUCCESS - If the allocation would succeed without compaction |
|
* COMPACT_CONTINUE - If compaction should run now |
|
*/ |
|
enum compact_result compaction_suitable(struct zone *zone, int order, |
|
unsigned int alloc_flags, |
|
int highest_zoneidx) |
|
{ |
|
enum compact_result ret; |
|
int fragindex; |
|
|
|
ret = __compaction_suitable(zone, order, alloc_flags, highest_zoneidx, |
|
zone_page_state(zone, NR_FREE_PAGES)); |
|
/* |
|
* fragmentation index determines if allocation failures are due to |
|
* low memory or external fragmentation |
|
* |
|
* index of -1000 would imply allocations might succeed depending on |
|
* watermarks, but we already failed the high-order watermark check |
|
* index towards 0 implies failure is due to lack of memory |
|
* index towards 1000 implies failure is due to fragmentation |
|
* |
|
* Only compact if a failure would be due to fragmentation. Also |
|
* ignore fragindex for non-costly orders where the alternative to |
|
* a successful reclaim/compaction is OOM. Fragindex and the |
|
* vm.extfrag_threshold sysctl is meant as a heuristic to prevent |
|
* excessive compaction for costly orders, but it should not be at the |
|
* expense of system stability. |
|
*/ |
|
if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) { |
|
fragindex = fragmentation_index(zone, order); |
|
if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) |
|
ret = COMPACT_NOT_SUITABLE_ZONE; |
|
} |
|
|
|
trace_mm_compaction_suitable(zone, order, ret); |
|
if (ret == COMPACT_NOT_SUITABLE_ZONE) |
|
ret = COMPACT_SKIPPED; |
|
|
|
return ret; |
|
} |
|
|
|
bool compaction_zonelist_suitable(struct alloc_context *ac, int order, |
|
int alloc_flags) |
|
{ |
|
struct zone *zone; |
|
struct zoneref *z; |
|
|
|
/* |
|
* Make sure at least one zone would pass __compaction_suitable if we continue |
|
* retrying the reclaim. |
|
*/ |
|
for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, |
|
ac->highest_zoneidx, ac->nodemask) { |
|
unsigned long available; |
|
enum compact_result compact_result; |
|
|
|
/* |
|
* Do not consider all the reclaimable memory because we do not |
|
* want to trash just for a single high order allocation which |
|
* is even not guaranteed to appear even if __compaction_suitable |
|
* is happy about the watermark check. |
|
*/ |
|
available = zone_reclaimable_pages(zone) / order; |
|
available += zone_page_state_snapshot(zone, NR_FREE_PAGES); |
|
compact_result = __compaction_suitable(zone, order, alloc_flags, |
|
ac->highest_zoneidx, available); |
|
if (compact_result == COMPACT_CONTINUE) |
|
return true; |
|
} |
|
|
|
return false; |
|
} |
|
|
|
static enum compact_result |
|
compact_zone(struct compact_control *cc, struct capture_control *capc) |
|
{ |
|
enum compact_result ret; |
|
unsigned long start_pfn = cc->zone->zone_start_pfn; |
|
unsigned long end_pfn = zone_end_pfn(cc->zone); |
|
unsigned long last_migrated_pfn; |
|
const bool sync = cc->mode != MIGRATE_ASYNC; |
|
bool update_cached; |
|
unsigned int nr_succeeded = 0; |
|
|
|
/* |
|
* These counters track activities during zone compaction. Initialize |
|
* them before compacting a new zone. |
|
*/ |
|
cc->total_migrate_scanned = 0; |
|
cc->total_free_scanned = 0; |
|
cc->nr_migratepages = 0; |
|
cc->nr_freepages = 0; |
|
INIT_LIST_HEAD(&cc->freepages); |
|
INIT_LIST_HEAD(&cc->migratepages); |
|
|
|
cc->migratetype = gfp_migratetype(cc->gfp_mask); |
|
ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags, |
|
cc->highest_zoneidx); |
|
/* Compaction is likely to fail */ |
|
if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED) |
|
return ret; |
|
|
|
/* huh, compaction_suitable is returning something unexpected */ |
|
VM_BUG_ON(ret != COMPACT_CONTINUE); |
|
|
|
/* |
|
* Clear pageblock skip if there were failures recently and compaction |
|
* is about to be retried after being deferred. |
|
*/ |
|
if (compaction_restarting(cc->zone, cc->order)) |
|
__reset_isolation_suitable(cc->zone); |
|
|
|
/* |
|
* Setup to move all movable pages to the end of the zone. Used cached |
|
* information on where the scanners should start (unless we explicitly |
|
* want to compact the whole zone), but check that it is initialised |
|
* by ensuring the values are within zone boundaries. |
|
*/ |
|
cc->fast_start_pfn = 0; |
|
if (cc->whole_zone) { |
|
cc->migrate_pfn = start_pfn; |
|
cc->free_pfn = pageblock_start_pfn(end_pfn - 1); |
|
} else { |
|
cc->migrate_pfn = cc->zone->compact_cached_migrate_pfn[sync]; |
|
cc->free_pfn = cc->zone->compact_cached_free_pfn; |
|
if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) { |
|
cc->free_pfn = pageblock_start_pfn(end_pfn - 1); |
|
cc->zone->compact_cached_free_pfn = cc->free_pfn; |
|
} |
|
if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) { |
|
cc->migrate_pfn = start_pfn; |
|
cc->zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn; |
|
cc->zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn; |
|
} |
|
|
|
if (cc->migrate_pfn <= cc->zone->compact_init_migrate_pfn) |
|
cc->whole_zone = true; |
|
} |
|
|
|
last_migrated_pfn = 0; |
|
|
|
/* |
|
* Migrate has separate cached PFNs for ASYNC and SYNC* migration on |
|
* the basis that some migrations will fail in ASYNC mode. However, |
|
* if the cached PFNs match and pageblocks are skipped due to having |
|
* no isolation candidates, then the sync state does not matter. |
|
* Until a pageblock with isolation candidates is found, keep the |
|
* cached PFNs in sync to avoid revisiting the same blocks. |
|
*/ |
|
update_cached = !sync && |
|
cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1]; |
|
|
|
trace_mm_compaction_begin(cc, start_pfn, end_pfn, sync); |
|
|
|
/* lru_add_drain_all could be expensive with involving other CPUs */ |
|
lru_add_drain(); |
|
|
|
while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) { |
|
int err; |
|
unsigned long iteration_start_pfn = cc->migrate_pfn; |
|
|
|
/* |
|
* Avoid multiple rescans which can happen if a page cannot be |
|
* isolated (dirty/writeback in async mode) or if the migrated |
|
* pages are being allocated before the pageblock is cleared. |
|
* The first rescan will capture the entire pageblock for |
|
* migration. If it fails, it'll be marked skip and scanning |
|
* will proceed as normal. |
|
*/ |
|
cc->rescan = false; |
|
if (pageblock_start_pfn(last_migrated_pfn) == |
|
pageblock_start_pfn(iteration_start_pfn)) { |
|
cc->rescan = true; |
|
} |
|
|
|
switch (isolate_migratepages(cc)) { |
|
case ISOLATE_ABORT: |
|
ret = COMPACT_CONTENDED; |
|
putback_movable_pages(&cc->migratepages); |
|
cc->nr_migratepages = 0; |
|
goto out; |
|
case ISOLATE_NONE: |
|
if (update_cached) { |
|
cc->zone->compact_cached_migrate_pfn[1] = |
|
cc->zone->compact_cached_migrate_pfn[0]; |
|
} |
|
|
|
/* |
|
* We haven't isolated and migrated anything, but |
|
* there might still be unflushed migrations from |
|
* previous cc->order aligned block. |
|
*/ |
|
goto check_drain; |
|
case ISOLATE_SUCCESS: |
|
update_cached = false; |
|
last_migrated_pfn = iteration_start_pfn; |
|
} |
|
|
|
err = migrate_pages(&cc->migratepages, compaction_alloc, |
|
compaction_free, (unsigned long)cc, cc->mode, |
|
MR_COMPACTION, &nr_succeeded); |
|
|
|
trace_mm_compaction_migratepages(cc, nr_succeeded); |
|
|
|
/* All pages were either migrated or will be released */ |
|
cc->nr_migratepages = 0; |
|
if (err) { |
|
putback_movable_pages(&cc->migratepages); |
|
/* |
|
* migrate_pages() may return -ENOMEM when scanners meet |
|
* and we want compact_finished() to detect it |
|
*/ |
|
if (err == -ENOMEM && !compact_scanners_met(cc)) { |
|
ret = COMPACT_CONTENDED; |
|
goto out; |
|
} |
|
/* |
|
* We failed to migrate at least one page in the current |
|
* order-aligned block, so skip the rest of it. |
|
*/ |
|
if (cc->direct_compaction && |
|
(cc->mode == MIGRATE_ASYNC)) { |
|
cc->migrate_pfn = block_end_pfn( |
|
cc->migrate_pfn - 1, cc->order); |
|
/* Draining pcplists is useless in this case */ |
|
last_migrated_pfn = 0; |
|
} |
|
} |
|
|
|
check_drain: |
|
/* |
|
* Has the migration scanner moved away from the previous |
|
* cc->order aligned block where we migrated from? If yes, |
|
* flush the pages that were freed, so that they can merge and |
|
* compact_finished() can detect immediately if allocation |
|
* would succeed. |
|
*/ |
|
if (cc->order > 0 && last_migrated_pfn) { |
|
unsigned long current_block_start = |
|
block_start_pfn(cc->migrate_pfn, cc->order); |
|
|
|
if (last_migrated_pfn < current_block_start) { |
|
lru_add_drain_cpu_zone(cc->zone); |
|
/* No more flushing until we migrate again */ |
|
last_migrated_pfn = 0; |
|
} |
|
} |
|
|
|
/* Stop if a page has been captured */ |
|
if (capc && capc->page) { |
|
ret = COMPACT_SUCCESS; |
|
break; |
|
} |
|
} |
|
|
|
out: |
|
/* |
|
* Release free pages and update where the free scanner should restart, |
|
* so we don't leave any returned pages behind in the next attempt. |
|
*/ |
|
if (cc->nr_freepages > 0) { |
|
unsigned long free_pfn = release_freepages(&cc->freepages); |
|
|
|
cc->nr_freepages = 0; |
|
VM_BUG_ON(free_pfn == 0); |
|
/* The cached pfn is always the first in a pageblock */ |
|
free_pfn = pageblock_start_pfn(free_pfn); |
|
/* |
|
* Only go back, not forward. The cached pfn might have been |
|
* already reset to zone end in compact_finished() |
|
*/ |
|
if (free_pfn > cc->zone->compact_cached_free_pfn) |
|
cc->zone->compact_cached_free_pfn = free_pfn; |
|
} |
|
|
|
count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned); |
|
count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned); |
|
|
|
trace_mm_compaction_end(cc, start_pfn, end_pfn, sync, ret); |
|
|
|
return ret; |
|
} |
|
|
|
static enum compact_result compact_zone_order(struct zone *zone, int order, |
|
gfp_t gfp_mask, enum compact_priority prio, |
|
unsigned int alloc_flags, int highest_zoneidx, |
|
struct page **capture) |
|
{ |
|
enum compact_result ret; |
|
struct compact_control cc = { |
|
.order = order, |
|
.search_order = order, |
|
.gfp_mask = gfp_mask, |
|
.zone = zone, |
|
.mode = (prio == COMPACT_PRIO_ASYNC) ? |
|
MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT, |
|
.alloc_flags = alloc_flags, |
|
.highest_zoneidx = highest_zoneidx, |
|
.direct_compaction = true, |
|
.whole_zone = (prio == MIN_COMPACT_PRIORITY), |
|
.ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY), |
|
.ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY) |
|
}; |
|
struct capture_control capc = { |
|
.cc = &cc, |
|
.page = NULL, |
|
}; |
|
|
|
/* |
|
* Make sure the structs are really initialized before we expose the |
|
* capture control, in case we are interrupted and the interrupt handler |
|
* frees a page. |
|
*/ |
|
barrier(); |
|
WRITE_ONCE(current->capture_control, &capc); |
|
|
|
ret = compact_zone(&cc, &capc); |
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages)); |
|
VM_BUG_ON(!list_empty(&cc.migratepages)); |
|
|
|
/* |
|
* Make sure we hide capture control first before we read the captured |
|
* page pointer, otherwise an interrupt could free and capture a page |
|
* and we would leak it. |
|
*/ |
|
WRITE_ONCE(current->capture_control, NULL); |
|
*capture = READ_ONCE(capc.page); |
|
/* |
|
* Technically, it is also possible that compaction is skipped but |
|
* the page is still captured out of luck(IRQ came and freed the page). |
|
* Returning COMPACT_SUCCESS in such cases helps in properly accounting |
|
* the COMPACT[STALL|FAIL] when compaction is skipped. |
|
*/ |
|
if (*capture) |
|
ret = COMPACT_SUCCESS; |
|
|
|
return ret; |
|
} |
|
|
|
int sysctl_extfrag_threshold = 500; |
|
|
|
/** |
|
* try_to_compact_pages - Direct compact to satisfy a high-order allocation |
|
* @gfp_mask: The GFP mask of the current allocation |
|
* @order: The order of the current allocation |
|
* @alloc_flags: The allocation flags of the current allocation |
|
* @ac: The context of current allocation |
|
* @prio: Determines how hard direct compaction should try to succeed |
|
* @capture: Pointer to free page created by compaction will be stored here |
|
* |
|
* This is the main entry point for direct page compaction. |
|
*/ |
|
enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, |
|
unsigned int alloc_flags, const struct alloc_context *ac, |
|
enum compact_priority prio, struct page **capture) |
|
{ |
|
int may_perform_io = (__force int)(gfp_mask & __GFP_IO); |
|
struct zoneref *z; |
|
struct zone *zone; |
|
enum compact_result rc = COMPACT_SKIPPED; |
|
|
|
/* |
|
* Check if the GFP flags allow compaction - GFP_NOIO is really |
|
* tricky context because the migration might require IO |
|
*/ |
|
if (!may_perform_io) |
|
return COMPACT_SKIPPED; |
|
|
|
trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio); |
|
|
|
/* Compact each zone in the list */ |
|
for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, |
|
ac->highest_zoneidx, ac->nodemask) { |
|
enum compact_result status; |
|
|
|
if (prio > MIN_COMPACT_PRIORITY |
|
&& compaction_deferred(zone, order)) { |
|
rc = max_t(enum compact_result, COMPACT_DEFERRED, rc); |
|
continue; |
|
} |
|
|
|
status = compact_zone_order(zone, order, gfp_mask, prio, |
|
alloc_flags, ac->highest_zoneidx, capture); |
|
rc = max(status, rc); |
|
|
|
/* The allocation should succeed, stop compacting */ |
|
if (status == COMPACT_SUCCESS) { |
|
/* |
|
* We think the allocation will succeed in this zone, |
|
* but it is not certain, hence the false. The caller |
|
* will repeat this with true if allocation indeed |
|
* succeeds in this zone. |
|
*/ |
|
compaction_defer_reset(zone, order, false); |
|
|
|
break; |
|
} |
|
|
|
if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE || |
|
status == COMPACT_PARTIAL_SKIPPED)) |
|
/* |
|
* We think that allocation won't succeed in this zone |
|
* so we defer compaction there. If it ends up |
|
* succeeding after all, it will be reset. |
|
*/ |
|
defer_compaction(zone, order); |
|
|
|
/* |
|
* We might have stopped compacting due to need_resched() in |
|
* async compaction, or due to a fatal signal detected. In that |
|
* case do not try further zones |
|
*/ |
|
if ((prio == COMPACT_PRIO_ASYNC && need_resched()) |
|
|| fatal_signal_pending(current)) |
|
break; |
|
} |
|
|
|
return rc; |
|
} |
|
|
|
/* |
|
* Compact all zones within a node till each zone's fragmentation score |
|
* reaches within proactive compaction thresholds (as determined by the |
|
* proactiveness tunable). |
|
* |
|
* It is possible that the function returns before reaching score targets |
|
* due to various back-off conditions, such as, contention on per-node or |
|
* per-zone locks. |
|
*/ |
|
static void proactive_compact_node(pg_data_t *pgdat) |
|
{ |
|
int zoneid; |
|
struct zone *zone; |
|
struct compact_control cc = { |
|
.order = -1, |
|
.mode = MIGRATE_SYNC_LIGHT, |
|
.ignore_skip_hint = true, |
|
.whole_zone = true, |
|
.gfp_mask = GFP_KERNEL, |
|
.proactive_compaction = true, |
|
}; |
|
|
|
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
|
zone = &pgdat->node_zones[zoneid]; |
|
if (!populated_zone(zone)) |
|
continue; |
|
|
|
cc.zone = zone; |
|
|
|
compact_zone(&cc, NULL); |
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages)); |
|
VM_BUG_ON(!list_empty(&cc.migratepages)); |
|
} |
|
} |
|
|
|
/* Compact all zones within a node */ |
|
static void compact_node(int nid) |
|
{ |
|
pg_data_t *pgdat = NODE_DATA(nid); |
|
int zoneid; |
|
struct zone *zone; |
|
struct compact_control cc = { |
|
.order = -1, |
|
.mode = MIGRATE_SYNC, |
|
.ignore_skip_hint = true, |
|
.whole_zone = true, |
|
.gfp_mask = GFP_KERNEL, |
|
}; |
|
|
|
|
|
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
|
|
|
zone = &pgdat->node_zones[zoneid]; |
|
if (!populated_zone(zone)) |
|
continue; |
|
|
|
cc.zone = zone; |
|
|
|
compact_zone(&cc, NULL); |
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages)); |
|
VM_BUG_ON(!list_empty(&cc.migratepages)); |
|
} |
|
} |
|
|
|
/* Compact all nodes in the system */ |
|
static void compact_nodes(void) |
|
{ |
|
int nid; |
|
|
|
/* Flush pending updates to the LRU lists */ |
|
lru_add_drain_all(); |
|
|
|
for_each_online_node(nid) |
|
compact_node(nid); |
|
} |
|
|
|
/* |
|
* Tunable for proactive compaction. It determines how |
|
* aggressively the kernel should compact memory in the |
|
* background. It takes values in the range [0, 100]. |
|
*/ |
|
unsigned int __read_mostly sysctl_compaction_proactiveness = 20; |
|
|
|
int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write, |
|
void *buffer, size_t *length, loff_t *ppos) |
|
{ |
|
int rc, nid; |
|
|
|
rc = proc_dointvec_minmax(table, write, buffer, length, ppos); |
|
if (rc) |
|
return rc; |
|
|
|
if (write && sysctl_compaction_proactiveness) { |
|
for_each_online_node(nid) { |
|
pg_data_t *pgdat = NODE_DATA(nid); |
|
|
|
if (pgdat->proactive_compact_trigger) |
|
continue; |
|
|
|
pgdat->proactive_compact_trigger = true; |
|
wake_up_interruptible(&pgdat->kcompactd_wait); |
|
} |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* This is the entry point for compacting all nodes via |
|
* /proc/sys/vm/compact_memory |
|
*/ |
|
int sysctl_compaction_handler(struct ctl_table *table, int write, |
|
void *buffer, size_t *length, loff_t *ppos) |
|
{ |
|
if (write) |
|
compact_nodes(); |
|
|
|
return 0; |
|
} |
|
|
|
#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) |
|
static ssize_t compact_store(struct device *dev, |
|
struct device_attribute *attr, |
|
const char *buf, size_t count) |
|
{ |
|
int nid = dev->id; |
|
|
|
if (nid >= 0 && nid < nr_node_ids && node_online(nid)) { |
|
/* Flush pending updates to the LRU lists */ |
|
lru_add_drain_all(); |
|
|
|
compact_node(nid); |
|
} |
|
|
|
return count; |
|
} |
|
static DEVICE_ATTR_WO(compact); |
|
|
|
int compaction_register_node(struct node *node) |
|
{ |
|
return device_create_file(&node->dev, &dev_attr_compact); |
|
} |
|
|
|
void compaction_unregister_node(struct node *node) |
|
{ |
|
return device_remove_file(&node->dev, &dev_attr_compact); |
|
} |
|
#endif /* CONFIG_SYSFS && CONFIG_NUMA */ |
|
|
|
static inline bool kcompactd_work_requested(pg_data_t *pgdat) |
|
{ |
|
return pgdat->kcompactd_max_order > 0 || kthread_should_stop() || |
|
pgdat->proactive_compact_trigger; |
|
} |
|
|
|
static bool kcompactd_node_suitable(pg_data_t *pgdat) |
|
{ |
|
int zoneid; |
|
struct zone *zone; |
|
enum zone_type highest_zoneidx = pgdat->kcompactd_highest_zoneidx; |
|
|
|
for (zoneid = 0; zoneid <= highest_zoneidx; zoneid++) { |
|
zone = &pgdat->node_zones[zoneid]; |
|
|
|
if (!populated_zone(zone)) |
|
continue; |
|
|
|
if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0, |
|
highest_zoneidx) == COMPACT_CONTINUE) |
|
return true; |
|
} |
|
|
|
return false; |
|
} |
|
|
|
static void kcompactd_do_work(pg_data_t *pgdat) |
|
{ |
|
/* |
|
* With no special task, compact all zones so that a page of requested |
|
* order is allocatable. |
|
*/ |
|
int zoneid; |
|
struct zone *zone; |
|
struct compact_control cc = { |
|
.order = pgdat->kcompactd_max_order, |
|
.search_order = pgdat->kcompactd_max_order, |
|
.highest_zoneidx = pgdat->kcompactd_highest_zoneidx, |
|
.mode = MIGRATE_SYNC_LIGHT, |
|
.ignore_skip_hint = false, |
|
.gfp_mask = GFP_KERNEL, |
|
}; |
|
trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order, |
|
cc.highest_zoneidx); |
|
count_compact_event(KCOMPACTD_WAKE); |
|
|
|
for (zoneid = 0; zoneid <= cc.highest_zoneidx; zoneid++) { |
|
int status; |
|
|
|
zone = &pgdat->node_zones[zoneid]; |
|
if (!populated_zone(zone)) |
|
continue; |
|
|
|
if (compaction_deferred(zone, cc.order)) |
|
continue; |
|
|
|
if (compaction_suitable(zone, cc.order, 0, zoneid) != |
|
COMPACT_CONTINUE) |
|
continue; |
|
|
|
if (kthread_should_stop()) |
|
return; |
|
|
|
cc.zone = zone; |
|
status = compact_zone(&cc, NULL); |
|
|
|
if (status == COMPACT_SUCCESS) { |
|
compaction_defer_reset(zone, cc.order, false); |
|
} else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) { |
|
/* |
|
* Buddy pages may become stranded on pcps that could |
|
* otherwise coalesce on the zone's free area for |
|
* order >= cc.order. This is ratelimited by the |
|
* upcoming deferral. |
|
*/ |
|
drain_all_pages(zone); |
|
|
|
/* |
|
* We use sync migration mode here, so we defer like |
|
* sync direct compaction does. |
|
*/ |
|
defer_compaction(zone, cc.order); |
|
} |
|
|
|
count_compact_events(KCOMPACTD_MIGRATE_SCANNED, |
|
cc.total_migrate_scanned); |
|
count_compact_events(KCOMPACTD_FREE_SCANNED, |
|
cc.total_free_scanned); |
|
|
|
VM_BUG_ON(!list_empty(&cc.freepages)); |
|
VM_BUG_ON(!list_empty(&cc.migratepages)); |
|
} |
|
|
|
/* |
|
* Regardless of success, we are done until woken up next. But remember |
|
* the requested order/highest_zoneidx in case it was higher/tighter |
|
* than our current ones |
|
*/ |
|
if (pgdat->kcompactd_max_order <= cc.order) |
|
pgdat->kcompactd_max_order = 0; |
|
if (pgdat->kcompactd_highest_zoneidx >= cc.highest_zoneidx) |
|
pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1; |
|
} |
|
|
|
void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx) |
|
{ |
|
if (!order) |
|
return; |
|
|
|
if (pgdat->kcompactd_max_order < order) |
|
pgdat->kcompactd_max_order = order; |
|
|
|
if (pgdat->kcompactd_highest_zoneidx > highest_zoneidx) |
|
pgdat->kcompactd_highest_zoneidx = highest_zoneidx; |
|
|
|
/* |
|
* Pairs with implicit barrier in wait_event_freezable() |
|
* such that wakeups are not missed. |
|
*/ |
|
if (!wq_has_sleeper(&pgdat->kcompactd_wait)) |
|
return; |
|
|
|
if (!kcompactd_node_suitable(pgdat)) |
|
return; |
|
|
|
trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order, |
|
highest_zoneidx); |
|
wake_up_interruptible(&pgdat->kcompactd_wait); |
|
} |
|
|
|
/* |
|
* The background compaction daemon, started as a kernel thread |
|
* from the init process. |
|
*/ |
|
static int kcompactd(void *p) |
|
{ |
|
pg_data_t *pgdat = (pg_data_t *)p; |
|
struct task_struct *tsk = current; |
|
long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC); |
|
long timeout = default_timeout; |
|
|
|
const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
|
|
|
if (!cpumask_empty(cpumask)) |
|
set_cpus_allowed_ptr(tsk, cpumask); |
|
|
|
set_freezable(); |
|
|
|
pgdat->kcompactd_max_order = 0; |
|
pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1; |
|
|
|
while (!kthread_should_stop()) { |
|
unsigned long pflags; |
|
|
|
/* |
|
* Avoid the unnecessary wakeup for proactive compaction |
|
* when it is disabled. |
|
*/ |
|
if (!sysctl_compaction_proactiveness) |
|
timeout = MAX_SCHEDULE_TIMEOUT; |
|
trace_mm_compaction_kcompactd_sleep(pgdat->node_id); |
|
if (wait_event_freezable_timeout(pgdat->kcompactd_wait, |
|
kcompactd_work_requested(pgdat), timeout) && |
|
!pgdat->proactive_compact_trigger) { |
|
|
|
psi_memstall_enter(&pflags); |
|
kcompactd_do_work(pgdat); |
|
psi_memstall_leave(&pflags); |
|
/* |
|
* Reset the timeout value. The defer timeout from |
|
* proactive compaction is lost here but that is fine |
|
* as the condition of the zone changing substantionally |
|
* then carrying on with the previous defer interval is |
|
* not useful. |
|
*/ |
|
timeout = default_timeout; |
|
continue; |
|
} |
|
|
|
/* |
|
* Start the proactive work with default timeout. Based |
|
* on the fragmentation score, this timeout is updated. |
|
*/ |
|
timeout = default_timeout; |
|
if (should_proactive_compact_node(pgdat)) { |
|
unsigned int prev_score, score; |
|
|
|
prev_score = fragmentation_score_node(pgdat); |
|
proactive_compact_node(pgdat); |
|
score = fragmentation_score_node(pgdat); |
|
/* |
|
* Defer proactive compaction if the fragmentation |
|
* score did not go down i.e. no progress made. |
|
*/ |
|
if (unlikely(score >= prev_score)) |
|
timeout = |
|
default_timeout << COMPACT_MAX_DEFER_SHIFT; |
|
} |
|
if (unlikely(pgdat->proactive_compact_trigger)) |
|
pgdat->proactive_compact_trigger = false; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* This kcompactd start function will be called by init and node-hot-add. |
|
* On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added. |
|
*/ |
|
void kcompactd_run(int nid) |
|
{ |
|
pg_data_t *pgdat = NODE_DATA(nid); |
|
|
|
if (pgdat->kcompactd) |
|
return; |
|
|
|
pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid); |
|
if (IS_ERR(pgdat->kcompactd)) { |
|
pr_err("Failed to start kcompactd on node %d\n", nid); |
|
pgdat->kcompactd = NULL; |
|
} |
|
} |
|
|
|
/* |
|
* Called by memory hotplug when all memory in a node is offlined. Caller must |
|
* be holding mem_hotplug_begin/done(). |
|
*/ |
|
void kcompactd_stop(int nid) |
|
{ |
|
struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd; |
|
|
|
if (kcompactd) { |
|
kthread_stop(kcompactd); |
|
NODE_DATA(nid)->kcompactd = NULL; |
|
} |
|
} |
|
|
|
/* |
|
* It's optimal to keep kcompactd on the same CPUs as their memory, but |
|
* not required for correctness. So if the last cpu in a node goes |
|
* away, we get changed to run anywhere: as the first one comes back, |
|
* restore their cpu bindings. |
|
*/ |
|
static int kcompactd_cpu_online(unsigned int cpu) |
|
{ |
|
int nid; |
|
|
|
for_each_node_state(nid, N_MEMORY) { |
|
pg_data_t *pgdat = NODE_DATA(nid); |
|
const struct cpumask *mask; |
|
|
|
mask = cpumask_of_node(pgdat->node_id); |
|
|
|
if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
|
/* One of our CPUs online: restore mask */ |
|
if (pgdat->kcompactd) |
|
set_cpus_allowed_ptr(pgdat->kcompactd, mask); |
|
} |
|
return 0; |
|
} |
|
|
|
static int __init kcompactd_init(void) |
|
{ |
|
int nid; |
|
int ret; |
|
|
|
ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, |
|
"mm/compaction:online", |
|
kcompactd_cpu_online, NULL); |
|
if (ret < 0) { |
|
pr_err("kcompactd: failed to register hotplug callbacks.\n"); |
|
return ret; |
|
} |
|
|
|
for_each_node_state(nid, N_MEMORY) |
|
kcompactd_run(nid); |
|
return 0; |
|
} |
|
subsys_initcall(kcompactd_init) |
|
|
|
#endif /* CONFIG_COMPACTION */
|
|
|