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2354 lines
59 KiB
2354 lines
59 KiB
// SPDX-License-Identifier: GPL-2.0 |
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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#include <linux/mm.h> |
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#include <linux/sched.h> |
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#include <linux/sched/mm.h> |
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#include <linux/sched/coredump.h> |
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#include <linux/mmu_notifier.h> |
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#include <linux/rmap.h> |
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#include <linux/swap.h> |
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#include <linux/mm_inline.h> |
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#include <linux/kthread.h> |
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#include <linux/khugepaged.h> |
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#include <linux/freezer.h> |
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#include <linux/mman.h> |
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#include <linux/hashtable.h> |
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#include <linux/userfaultfd_k.h> |
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#include <linux/page_idle.h> |
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#include <linux/page_table_check.h> |
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#include <linux/swapops.h> |
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#include <linux/shmem_fs.h> |
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|
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#include <asm/tlb.h> |
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#include <asm/pgalloc.h> |
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#include "internal.h" |
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enum scan_result { |
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SCAN_FAIL, |
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SCAN_SUCCEED, |
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SCAN_PMD_NULL, |
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SCAN_EXCEED_NONE_PTE, |
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SCAN_EXCEED_SWAP_PTE, |
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SCAN_EXCEED_SHARED_PTE, |
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SCAN_PTE_NON_PRESENT, |
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SCAN_PTE_UFFD_WP, |
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SCAN_PAGE_RO, |
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SCAN_LACK_REFERENCED_PAGE, |
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SCAN_PAGE_NULL, |
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SCAN_SCAN_ABORT, |
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SCAN_PAGE_COUNT, |
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SCAN_PAGE_LRU, |
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SCAN_PAGE_LOCK, |
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SCAN_PAGE_ANON, |
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SCAN_PAGE_COMPOUND, |
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SCAN_ANY_PROCESS, |
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SCAN_VMA_NULL, |
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SCAN_VMA_CHECK, |
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SCAN_ADDRESS_RANGE, |
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SCAN_DEL_PAGE_LRU, |
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SCAN_ALLOC_HUGE_PAGE_FAIL, |
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SCAN_CGROUP_CHARGE_FAIL, |
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SCAN_TRUNCATED, |
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SCAN_PAGE_HAS_PRIVATE, |
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}; |
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#define CREATE_TRACE_POINTS |
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#include <trace/events/huge_memory.h> |
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|
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static struct task_struct *khugepaged_thread __read_mostly; |
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static DEFINE_MUTEX(khugepaged_mutex); |
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|
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/* default scan 8*512 pte (or vmas) every 30 second */ |
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static unsigned int khugepaged_pages_to_scan __read_mostly; |
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static unsigned int khugepaged_pages_collapsed; |
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static unsigned int khugepaged_full_scans; |
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static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; |
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/* during fragmentation poll the hugepage allocator once every minute */ |
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static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; |
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static unsigned long khugepaged_sleep_expire; |
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static DEFINE_SPINLOCK(khugepaged_mm_lock); |
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static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); |
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/* |
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* default collapse hugepages if there is at least one pte mapped like |
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* it would have happened if the vma was large enough during page |
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* fault. |
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*/ |
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static unsigned int khugepaged_max_ptes_none __read_mostly; |
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static unsigned int khugepaged_max_ptes_swap __read_mostly; |
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static unsigned int khugepaged_max_ptes_shared __read_mostly; |
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|
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#define MM_SLOTS_HASH_BITS 10 |
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static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); |
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static struct kmem_cache *mm_slot_cache __read_mostly; |
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#define MAX_PTE_MAPPED_THP 8 |
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/** |
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* struct mm_slot - hash lookup from mm to mm_slot |
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* @hash: hash collision list |
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* @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head |
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* @mm: the mm that this information is valid for |
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* @nr_pte_mapped_thp: number of pte mapped THP |
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* @pte_mapped_thp: address array corresponding pte mapped THP |
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*/ |
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struct mm_slot { |
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struct hlist_node hash; |
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struct list_head mm_node; |
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struct mm_struct *mm; |
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|
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/* pte-mapped THP in this mm */ |
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int nr_pte_mapped_thp; |
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unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP]; |
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}; |
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|
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/** |
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* struct khugepaged_scan - cursor for scanning |
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* @mm_head: the head of the mm list to scan |
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* @mm_slot: the current mm_slot we are scanning |
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* @address: the next address inside that to be scanned |
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* |
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* There is only the one khugepaged_scan instance of this cursor structure. |
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*/ |
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struct khugepaged_scan { |
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struct list_head mm_head; |
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struct mm_slot *mm_slot; |
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unsigned long address; |
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}; |
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static struct khugepaged_scan khugepaged_scan = { |
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.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), |
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}; |
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#ifdef CONFIG_SYSFS |
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static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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char *buf) |
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{ |
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return sysfs_emit(buf, "%u\n", khugepaged_scan_sleep_millisecs); |
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} |
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static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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unsigned int msecs; |
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int err; |
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|
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err = kstrtouint(buf, 10, &msecs); |
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if (err) |
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return -EINVAL; |
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khugepaged_scan_sleep_millisecs = msecs; |
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khugepaged_sleep_expire = 0; |
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wake_up_interruptible(&khugepaged_wait); |
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|
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return count; |
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} |
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static struct kobj_attribute scan_sleep_millisecs_attr = |
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__ATTR_RW(scan_sleep_millisecs); |
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|
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static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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char *buf) |
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{ |
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return sysfs_emit(buf, "%u\n", khugepaged_alloc_sleep_millisecs); |
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} |
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static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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unsigned int msecs; |
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int err; |
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err = kstrtouint(buf, 10, &msecs); |
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if (err) |
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return -EINVAL; |
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khugepaged_alloc_sleep_millisecs = msecs; |
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khugepaged_sleep_expire = 0; |
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wake_up_interruptible(&khugepaged_wait); |
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return count; |
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} |
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static struct kobj_attribute alloc_sleep_millisecs_attr = |
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__ATTR_RW(alloc_sleep_millisecs); |
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static ssize_t pages_to_scan_show(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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char *buf) |
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{ |
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return sysfs_emit(buf, "%u\n", khugepaged_pages_to_scan); |
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} |
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static ssize_t pages_to_scan_store(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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unsigned int pages; |
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int err; |
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|
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err = kstrtouint(buf, 10, &pages); |
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if (err || !pages) |
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return -EINVAL; |
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khugepaged_pages_to_scan = pages; |
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|
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return count; |
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} |
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static struct kobj_attribute pages_to_scan_attr = |
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__ATTR_RW(pages_to_scan); |
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static ssize_t pages_collapsed_show(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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char *buf) |
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{ |
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return sysfs_emit(buf, "%u\n", khugepaged_pages_collapsed); |
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} |
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static struct kobj_attribute pages_collapsed_attr = |
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__ATTR_RO(pages_collapsed); |
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static ssize_t full_scans_show(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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char *buf) |
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{ |
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return sysfs_emit(buf, "%u\n", khugepaged_full_scans); |
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} |
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static struct kobj_attribute full_scans_attr = |
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__ATTR_RO(full_scans); |
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static ssize_t defrag_show(struct kobject *kobj, |
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struct kobj_attribute *attr, char *buf) |
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{ |
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return single_hugepage_flag_show(kobj, attr, buf, |
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TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); |
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} |
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static ssize_t defrag_store(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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return single_hugepage_flag_store(kobj, attr, buf, count, |
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TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); |
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} |
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static struct kobj_attribute khugepaged_defrag_attr = |
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__ATTR_RW(defrag); |
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|
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/* |
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* max_ptes_none controls if khugepaged should collapse hugepages over |
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* any unmapped ptes in turn potentially increasing the memory |
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* footprint of the vmas. When max_ptes_none is 0 khugepaged will not |
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* reduce the available free memory in the system as it |
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* runs. Increasing max_ptes_none will instead potentially reduce the |
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* free memory in the system during the khugepaged scan. |
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*/ |
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static ssize_t max_ptes_none_show(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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char *buf) |
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{ |
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return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_none); |
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} |
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static ssize_t max_ptes_none_store(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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int err; |
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unsigned long max_ptes_none; |
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err = kstrtoul(buf, 10, &max_ptes_none); |
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if (err || max_ptes_none > HPAGE_PMD_NR - 1) |
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return -EINVAL; |
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khugepaged_max_ptes_none = max_ptes_none; |
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return count; |
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} |
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static struct kobj_attribute khugepaged_max_ptes_none_attr = |
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__ATTR_RW(max_ptes_none); |
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static ssize_t max_ptes_swap_show(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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char *buf) |
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{ |
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return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_swap); |
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} |
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static ssize_t max_ptes_swap_store(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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int err; |
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unsigned long max_ptes_swap; |
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err = kstrtoul(buf, 10, &max_ptes_swap); |
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if (err || max_ptes_swap > HPAGE_PMD_NR - 1) |
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return -EINVAL; |
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khugepaged_max_ptes_swap = max_ptes_swap; |
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return count; |
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} |
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static struct kobj_attribute khugepaged_max_ptes_swap_attr = |
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__ATTR_RW(max_ptes_swap); |
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static ssize_t max_ptes_shared_show(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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char *buf) |
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{ |
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return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_shared); |
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} |
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static ssize_t max_ptes_shared_store(struct kobject *kobj, |
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struct kobj_attribute *attr, |
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const char *buf, size_t count) |
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{ |
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int err; |
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unsigned long max_ptes_shared; |
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err = kstrtoul(buf, 10, &max_ptes_shared); |
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if (err || max_ptes_shared > HPAGE_PMD_NR - 1) |
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return -EINVAL; |
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khugepaged_max_ptes_shared = max_ptes_shared; |
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return count; |
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} |
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static struct kobj_attribute khugepaged_max_ptes_shared_attr = |
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__ATTR_RW(max_ptes_shared); |
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static struct attribute *khugepaged_attr[] = { |
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&khugepaged_defrag_attr.attr, |
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&khugepaged_max_ptes_none_attr.attr, |
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&khugepaged_max_ptes_swap_attr.attr, |
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&khugepaged_max_ptes_shared_attr.attr, |
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&pages_to_scan_attr.attr, |
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&pages_collapsed_attr.attr, |
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&full_scans_attr.attr, |
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&scan_sleep_millisecs_attr.attr, |
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&alloc_sleep_millisecs_attr.attr, |
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NULL, |
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}; |
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struct attribute_group khugepaged_attr_group = { |
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.attrs = khugepaged_attr, |
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.name = "khugepaged", |
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}; |
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#endif /* CONFIG_SYSFS */ |
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|
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int hugepage_madvise(struct vm_area_struct *vma, |
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unsigned long *vm_flags, int advice) |
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{ |
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switch (advice) { |
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case MADV_HUGEPAGE: |
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#ifdef CONFIG_S390 |
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/* |
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* qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 |
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* can't handle this properly after s390_enable_sie, so we simply |
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* ignore the madvise to prevent qemu from causing a SIGSEGV. |
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*/ |
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if (mm_has_pgste(vma->vm_mm)) |
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return 0; |
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#endif |
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*vm_flags &= ~VM_NOHUGEPAGE; |
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*vm_flags |= VM_HUGEPAGE; |
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/* |
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* If the vma become good for khugepaged to scan, |
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* register it here without waiting a page fault that |
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* may not happen any time soon. |
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*/ |
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khugepaged_enter_vma(vma, *vm_flags); |
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break; |
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case MADV_NOHUGEPAGE: |
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*vm_flags &= ~VM_HUGEPAGE; |
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*vm_flags |= VM_NOHUGEPAGE; |
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/* |
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* Setting VM_NOHUGEPAGE will prevent khugepaged from scanning |
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* this vma even if we leave the mm registered in khugepaged if |
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* it got registered before VM_NOHUGEPAGE was set. |
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*/ |
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break; |
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} |
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return 0; |
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} |
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|
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int __init khugepaged_init(void) |
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{ |
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mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", |
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sizeof(struct mm_slot), |
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__alignof__(struct mm_slot), 0, NULL); |
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if (!mm_slot_cache) |
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return -ENOMEM; |
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khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; |
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khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; |
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khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; |
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khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2; |
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|
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return 0; |
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} |
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void __init khugepaged_destroy(void) |
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{ |
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kmem_cache_destroy(mm_slot_cache); |
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} |
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|
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static inline struct mm_slot *alloc_mm_slot(void) |
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{ |
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if (!mm_slot_cache) /* initialization failed */ |
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return NULL; |
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return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); |
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} |
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static inline void free_mm_slot(struct mm_slot *mm_slot) |
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{ |
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kmem_cache_free(mm_slot_cache, mm_slot); |
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} |
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static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
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{ |
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struct mm_slot *mm_slot; |
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|
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hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) |
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if (mm == mm_slot->mm) |
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return mm_slot; |
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|
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return NULL; |
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} |
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|
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static void insert_to_mm_slots_hash(struct mm_struct *mm, |
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struct mm_slot *mm_slot) |
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{ |
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mm_slot->mm = mm; |
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hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); |
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} |
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|
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static inline int khugepaged_test_exit(struct mm_struct *mm) |
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{ |
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return atomic_read(&mm->mm_users) == 0; |
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} |
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|
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void __khugepaged_enter(struct mm_struct *mm) |
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{ |
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struct mm_slot *mm_slot; |
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int wakeup; |
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|
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mm_slot = alloc_mm_slot(); |
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if (!mm_slot) |
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return; |
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|
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/* __khugepaged_exit() must not run from under us */ |
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VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); |
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if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { |
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free_mm_slot(mm_slot); |
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return; |
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} |
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|
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spin_lock(&khugepaged_mm_lock); |
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insert_to_mm_slots_hash(mm, mm_slot); |
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/* |
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* Insert just behind the scanning cursor, to let the area settle |
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* down a little. |
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*/ |
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wakeup = list_empty(&khugepaged_scan.mm_head); |
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list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); |
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spin_unlock(&khugepaged_mm_lock); |
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|
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mmgrab(mm); |
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if (wakeup) |
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wake_up_interruptible(&khugepaged_wait); |
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} |
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|
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void khugepaged_enter_vma(struct vm_area_struct *vma, |
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unsigned long vm_flags) |
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{ |
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if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) && |
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hugepage_flags_enabled()) { |
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if (hugepage_vma_check(vma, vm_flags, false, false)) |
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__khugepaged_enter(vma->vm_mm); |
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} |
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} |
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|
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void __khugepaged_exit(struct mm_struct *mm) |
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{ |
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struct mm_slot *mm_slot; |
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int free = 0; |
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|
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spin_lock(&khugepaged_mm_lock); |
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mm_slot = get_mm_slot(mm); |
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if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { |
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hash_del(&mm_slot->hash); |
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list_del(&mm_slot->mm_node); |
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free = 1; |
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} |
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spin_unlock(&khugepaged_mm_lock); |
|
|
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if (free) { |
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clear_bit(MMF_VM_HUGEPAGE, &mm->flags); |
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free_mm_slot(mm_slot); |
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mmdrop(mm); |
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} else if (mm_slot) { |
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/* |
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* This is required to serialize against |
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* khugepaged_test_exit() (which is guaranteed to run |
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* under mmap sem read mode). Stop here (after we |
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* return all pagetables will be destroyed) until |
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* khugepaged has finished working on the pagetables |
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* under the mmap_lock. |
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*/ |
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mmap_write_lock(mm); |
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mmap_write_unlock(mm); |
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} |
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} |
|
|
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static void release_pte_page(struct page *page) |
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{ |
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mod_node_page_state(page_pgdat(page), |
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NR_ISOLATED_ANON + page_is_file_lru(page), |
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-compound_nr(page)); |
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unlock_page(page); |
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putback_lru_page(page); |
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} |
|
|
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static void release_pte_pages(pte_t *pte, pte_t *_pte, |
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struct list_head *compound_pagelist) |
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{ |
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struct page *page, *tmp; |
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|
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while (--_pte >= pte) { |
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pte_t pteval = *_pte; |
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|
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page = pte_page(pteval); |
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if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) && |
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!PageCompound(page)) |
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release_pte_page(page); |
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} |
|
|
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list_for_each_entry_safe(page, tmp, compound_pagelist, lru) { |
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list_del(&page->lru); |
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release_pte_page(page); |
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} |
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} |
|
|
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static bool is_refcount_suitable(struct page *page) |
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{ |
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int expected_refcount; |
|
|
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expected_refcount = total_mapcount(page); |
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if (PageSwapCache(page)) |
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expected_refcount += compound_nr(page); |
|
|
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return page_count(page) == expected_refcount; |
|
} |
|
|
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static int __collapse_huge_page_isolate(struct vm_area_struct *vma, |
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unsigned long address, |
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pte_t *pte, |
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struct list_head *compound_pagelist) |
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{ |
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struct page *page = NULL; |
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pte_t *_pte; |
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int none_or_zero = 0, shared = 0, result = 0, referenced = 0; |
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bool writable = false; |
|
|
|
for (_pte = pte; _pte < pte + HPAGE_PMD_NR; |
|
_pte++, address += PAGE_SIZE) { |
|
pte_t pteval = *_pte; |
|
if (pte_none(pteval) || (pte_present(pteval) && |
|
is_zero_pfn(pte_pfn(pteval)))) { |
|
if (!userfaultfd_armed(vma) && |
|
++none_or_zero <= khugepaged_max_ptes_none) { |
|
continue; |
|
} else { |
|
result = SCAN_EXCEED_NONE_PTE; |
|
count_vm_event(THP_SCAN_EXCEED_NONE_PTE); |
|
goto out; |
|
} |
|
} |
|
if (!pte_present(pteval)) { |
|
result = SCAN_PTE_NON_PRESENT; |
|
goto out; |
|
} |
|
page = vm_normal_page(vma, address, pteval); |
|
if (unlikely(!page) || unlikely(is_zone_device_page(page))) { |
|
result = SCAN_PAGE_NULL; |
|
goto out; |
|
} |
|
|
|
VM_BUG_ON_PAGE(!PageAnon(page), page); |
|
|
|
if (page_mapcount(page) > 1 && |
|
++shared > khugepaged_max_ptes_shared) { |
|
result = SCAN_EXCEED_SHARED_PTE; |
|
count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); |
|
goto out; |
|
} |
|
|
|
if (PageCompound(page)) { |
|
struct page *p; |
|
page = compound_head(page); |
|
|
|
/* |
|
* Check if we have dealt with the compound page |
|
* already |
|
*/ |
|
list_for_each_entry(p, compound_pagelist, lru) { |
|
if (page == p) |
|
goto next; |
|
} |
|
} |
|
|
|
/* |
|
* We can do it before isolate_lru_page because the |
|
* page can't be freed from under us. NOTE: PG_lock |
|
* is needed to serialize against split_huge_page |
|
* when invoked from the VM. |
|
*/ |
|
if (!trylock_page(page)) { |
|
result = SCAN_PAGE_LOCK; |
|
goto out; |
|
} |
|
|
|
/* |
|
* Check if the page has any GUP (or other external) pins. |
|
* |
|
* The page table that maps the page has been already unlinked |
|
* from the page table tree and this process cannot get |
|
* an additional pin on the page. |
|
* |
|
* New pins can come later if the page is shared across fork, |
|
* but not from this process. The other process cannot write to |
|
* the page, only trigger CoW. |
|
*/ |
|
if (!is_refcount_suitable(page)) { |
|
unlock_page(page); |
|
result = SCAN_PAGE_COUNT; |
|
goto out; |
|
} |
|
|
|
/* |
|
* Isolate the page to avoid collapsing an hugepage |
|
* currently in use by the VM. |
|
*/ |
|
if (isolate_lru_page(page)) { |
|
unlock_page(page); |
|
result = SCAN_DEL_PAGE_LRU; |
|
goto out; |
|
} |
|
mod_node_page_state(page_pgdat(page), |
|
NR_ISOLATED_ANON + page_is_file_lru(page), |
|
compound_nr(page)); |
|
VM_BUG_ON_PAGE(!PageLocked(page), page); |
|
VM_BUG_ON_PAGE(PageLRU(page), page); |
|
|
|
if (PageCompound(page)) |
|
list_add_tail(&page->lru, compound_pagelist); |
|
next: |
|
/* There should be enough young pte to collapse the page */ |
|
if (pte_young(pteval) || |
|
page_is_young(page) || PageReferenced(page) || |
|
mmu_notifier_test_young(vma->vm_mm, address)) |
|
referenced++; |
|
|
|
if (pte_write(pteval)) |
|
writable = true; |
|
} |
|
|
|
if (unlikely(!writable)) { |
|
result = SCAN_PAGE_RO; |
|
} else if (unlikely(!referenced)) { |
|
result = SCAN_LACK_REFERENCED_PAGE; |
|
} else { |
|
result = SCAN_SUCCEED; |
|
trace_mm_collapse_huge_page_isolate(page, none_or_zero, |
|
referenced, writable, result); |
|
return 1; |
|
} |
|
out: |
|
release_pte_pages(pte, _pte, compound_pagelist); |
|
trace_mm_collapse_huge_page_isolate(page, none_or_zero, |
|
referenced, writable, result); |
|
return 0; |
|
} |
|
|
|
static void __collapse_huge_page_copy(pte_t *pte, struct page *page, |
|
struct vm_area_struct *vma, |
|
unsigned long address, |
|
spinlock_t *ptl, |
|
struct list_head *compound_pagelist) |
|
{ |
|
struct page *src_page, *tmp; |
|
pte_t *_pte; |
|
for (_pte = pte; _pte < pte + HPAGE_PMD_NR; |
|
_pte++, page++, address += PAGE_SIZE) { |
|
pte_t pteval = *_pte; |
|
|
|
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { |
|
clear_user_highpage(page, address); |
|
add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); |
|
if (is_zero_pfn(pte_pfn(pteval))) { |
|
/* |
|
* ptl mostly unnecessary. |
|
*/ |
|
spin_lock(ptl); |
|
ptep_clear(vma->vm_mm, address, _pte); |
|
spin_unlock(ptl); |
|
} |
|
} else { |
|
src_page = pte_page(pteval); |
|
copy_user_highpage(page, src_page, address, vma); |
|
if (!PageCompound(src_page)) |
|
release_pte_page(src_page); |
|
/* |
|
* ptl mostly unnecessary, but preempt has to |
|
* be disabled to update the per-cpu stats |
|
* inside page_remove_rmap(). |
|
*/ |
|
spin_lock(ptl); |
|
ptep_clear(vma->vm_mm, address, _pte); |
|
page_remove_rmap(src_page, vma, false); |
|
spin_unlock(ptl); |
|
free_page_and_swap_cache(src_page); |
|
} |
|
} |
|
|
|
list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) { |
|
list_del(&src_page->lru); |
|
mod_node_page_state(page_pgdat(src_page), |
|
NR_ISOLATED_ANON + page_is_file_lru(src_page), |
|
-compound_nr(src_page)); |
|
unlock_page(src_page); |
|
free_swap_cache(src_page); |
|
putback_lru_page(src_page); |
|
} |
|
} |
|
|
|
static void khugepaged_alloc_sleep(void) |
|
{ |
|
DEFINE_WAIT(wait); |
|
|
|
add_wait_queue(&khugepaged_wait, &wait); |
|
freezable_schedule_timeout_interruptible( |
|
msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); |
|
remove_wait_queue(&khugepaged_wait, &wait); |
|
} |
|
|
|
static int khugepaged_node_load[MAX_NUMNODES]; |
|
|
|
static bool khugepaged_scan_abort(int nid) |
|
{ |
|
int i; |
|
|
|
/* |
|
* If node_reclaim_mode is disabled, then no extra effort is made to |
|
* allocate memory locally. |
|
*/ |
|
if (!node_reclaim_enabled()) |
|
return false; |
|
|
|
/* If there is a count for this node already, it must be acceptable */ |
|
if (khugepaged_node_load[nid]) |
|
return false; |
|
|
|
for (i = 0; i < MAX_NUMNODES; i++) { |
|
if (!khugepaged_node_load[i]) |
|
continue; |
|
if (node_distance(nid, i) > node_reclaim_distance) |
|
return true; |
|
} |
|
return false; |
|
} |
|
|
|
#define khugepaged_defrag() \ |
|
(transparent_hugepage_flags & \ |
|
(1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)) |
|
|
|
/* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ |
|
static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) |
|
{ |
|
return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; |
|
} |
|
|
|
#ifdef CONFIG_NUMA |
|
static int khugepaged_find_target_node(void) |
|
{ |
|
static int last_khugepaged_target_node = NUMA_NO_NODE; |
|
int nid, target_node = 0, max_value = 0; |
|
|
|
/* find first node with max normal pages hit */ |
|
for (nid = 0; nid < MAX_NUMNODES; nid++) |
|
if (khugepaged_node_load[nid] > max_value) { |
|
max_value = khugepaged_node_load[nid]; |
|
target_node = nid; |
|
} |
|
|
|
/* do some balance if several nodes have the same hit record */ |
|
if (target_node <= last_khugepaged_target_node) |
|
for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; |
|
nid++) |
|
if (max_value == khugepaged_node_load[nid]) { |
|
target_node = nid; |
|
break; |
|
} |
|
|
|
last_khugepaged_target_node = target_node; |
|
return target_node; |
|
} |
|
|
|
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) |
|
{ |
|
if (IS_ERR(*hpage)) { |
|
if (!*wait) |
|
return false; |
|
|
|
*wait = false; |
|
*hpage = NULL; |
|
khugepaged_alloc_sleep(); |
|
} else if (*hpage) { |
|
put_page(*hpage); |
|
*hpage = NULL; |
|
} |
|
|
|
return true; |
|
} |
|
|
|
static struct page * |
|
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
|
{ |
|
VM_BUG_ON_PAGE(*hpage, *hpage); |
|
|
|
*hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); |
|
if (unlikely(!*hpage)) { |
|
count_vm_event(THP_COLLAPSE_ALLOC_FAILED); |
|
*hpage = ERR_PTR(-ENOMEM); |
|
return NULL; |
|
} |
|
|
|
prep_transhuge_page(*hpage); |
|
count_vm_event(THP_COLLAPSE_ALLOC); |
|
return *hpage; |
|
} |
|
#else |
|
static int khugepaged_find_target_node(void) |
|
{ |
|
return 0; |
|
} |
|
|
|
static inline struct page *alloc_khugepaged_hugepage(void) |
|
{ |
|
struct page *page; |
|
|
|
page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), |
|
HPAGE_PMD_ORDER); |
|
if (page) |
|
prep_transhuge_page(page); |
|
return page; |
|
} |
|
|
|
static struct page *khugepaged_alloc_hugepage(bool *wait) |
|
{ |
|
struct page *hpage; |
|
|
|
do { |
|
hpage = alloc_khugepaged_hugepage(); |
|
if (!hpage) { |
|
count_vm_event(THP_COLLAPSE_ALLOC_FAILED); |
|
if (!*wait) |
|
return NULL; |
|
|
|
*wait = false; |
|
khugepaged_alloc_sleep(); |
|
} else |
|
count_vm_event(THP_COLLAPSE_ALLOC); |
|
} while (unlikely(!hpage) && likely(hugepage_flags_enabled())); |
|
|
|
return hpage; |
|
} |
|
|
|
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) |
|
{ |
|
/* |
|
* If the hpage allocated earlier was briefly exposed in page cache |
|
* before collapse_file() failed, it is possible that racing lookups |
|
* have not yet completed, and would then be unpleasantly surprised by |
|
* finding the hpage reused for the same mapping at a different offset. |
|
* Just release the previous allocation if there is any danger of that. |
|
*/ |
|
if (*hpage && page_count(*hpage) > 1) { |
|
put_page(*hpage); |
|
*hpage = NULL; |
|
} |
|
|
|
if (!*hpage) |
|
*hpage = khugepaged_alloc_hugepage(wait); |
|
|
|
if (unlikely(!*hpage)) |
|
return false; |
|
|
|
return true; |
|
} |
|
|
|
static struct page * |
|
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
|
{ |
|
VM_BUG_ON(!*hpage); |
|
|
|
return *hpage; |
|
} |
|
#endif |
|
|
|
/* |
|
* If mmap_lock temporarily dropped, revalidate vma |
|
* before taking mmap_lock. |
|
* Return 0 if succeeds, otherwise return none-zero |
|
* value (scan code). |
|
*/ |
|
|
|
static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, |
|
struct vm_area_struct **vmap) |
|
{ |
|
struct vm_area_struct *vma; |
|
|
|
if (unlikely(khugepaged_test_exit(mm))) |
|
return SCAN_ANY_PROCESS; |
|
|
|
*vmap = vma = find_vma(mm, address); |
|
if (!vma) |
|
return SCAN_VMA_NULL; |
|
|
|
if (!transhuge_vma_suitable(vma, address)) |
|
return SCAN_ADDRESS_RANGE; |
|
if (!hugepage_vma_check(vma, vma->vm_flags, false, false)) |
|
return SCAN_VMA_CHECK; |
|
/* |
|
* Anon VMA expected, the address may be unmapped then |
|
* remapped to file after khugepaged reaquired the mmap_lock. |
|
* |
|
* hugepage_vma_check may return true for qualified file |
|
* vmas. |
|
*/ |
|
if (!vma->anon_vma || !vma_is_anonymous(vma)) |
|
return SCAN_VMA_CHECK; |
|
return 0; |
|
} |
|
|
|
/* |
|
* Bring missing pages in from swap, to complete THP collapse. |
|
* Only done if khugepaged_scan_pmd believes it is worthwhile. |
|
* |
|
* Called and returns without pte mapped or spinlocks held. |
|
* Note that if false is returned, mmap_lock will be released. |
|
*/ |
|
|
|
static bool __collapse_huge_page_swapin(struct mm_struct *mm, |
|
struct vm_area_struct *vma, |
|
unsigned long haddr, pmd_t *pmd, |
|
int referenced) |
|
{ |
|
int swapped_in = 0; |
|
vm_fault_t ret = 0; |
|
unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE); |
|
|
|
for (address = haddr; address < end; address += PAGE_SIZE) { |
|
struct vm_fault vmf = { |
|
.vma = vma, |
|
.address = address, |
|
.pgoff = linear_page_index(vma, haddr), |
|
.flags = FAULT_FLAG_ALLOW_RETRY, |
|
.pmd = pmd, |
|
}; |
|
|
|
vmf.pte = pte_offset_map(pmd, address); |
|
vmf.orig_pte = *vmf.pte; |
|
if (!is_swap_pte(vmf.orig_pte)) { |
|
pte_unmap(vmf.pte); |
|
continue; |
|
} |
|
ret = do_swap_page(&vmf); |
|
|
|
/* |
|
* do_swap_page returns VM_FAULT_RETRY with released mmap_lock. |
|
* Note we treat VM_FAULT_RETRY as VM_FAULT_ERROR here because |
|
* we do not retry here and swap entry will remain in pagetable |
|
* resulting in later failure. |
|
*/ |
|
if (ret & VM_FAULT_RETRY) { |
|
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
|
return false; |
|
} |
|
if (ret & VM_FAULT_ERROR) { |
|
mmap_read_unlock(mm); |
|
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
|
return false; |
|
} |
|
swapped_in++; |
|
} |
|
|
|
/* Drain LRU add pagevec to remove extra pin on the swapped in pages */ |
|
if (swapped_in) |
|
lru_add_drain(); |
|
|
|
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); |
|
return true; |
|
} |
|
|
|
static void collapse_huge_page(struct mm_struct *mm, |
|
unsigned long address, |
|
struct page **hpage, |
|
int node, int referenced, int unmapped) |
|
{ |
|
LIST_HEAD(compound_pagelist); |
|
pmd_t *pmd, _pmd; |
|
pte_t *pte; |
|
pgtable_t pgtable; |
|
struct page *new_page; |
|
spinlock_t *pmd_ptl, *pte_ptl; |
|
int isolated = 0, result = 0; |
|
struct vm_area_struct *vma; |
|
struct mmu_notifier_range range; |
|
gfp_t gfp; |
|
|
|
VM_BUG_ON(address & ~HPAGE_PMD_MASK); |
|
|
|
/* Only allocate from the target node */ |
|
gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
|
|
|
/* |
|
* Before allocating the hugepage, release the mmap_lock read lock. |
|
* The allocation can take potentially a long time if it involves |
|
* sync compaction, and we do not need to hold the mmap_lock during |
|
* that. We will recheck the vma after taking it again in write mode. |
|
*/ |
|
mmap_read_unlock(mm); |
|
new_page = khugepaged_alloc_page(hpage, gfp, node); |
|
if (!new_page) { |
|
result = SCAN_ALLOC_HUGE_PAGE_FAIL; |
|
goto out_nolock; |
|
} |
|
|
|
if (unlikely(mem_cgroup_charge(page_folio(new_page), mm, gfp))) { |
|
result = SCAN_CGROUP_CHARGE_FAIL; |
|
goto out_nolock; |
|
} |
|
count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC); |
|
|
|
mmap_read_lock(mm); |
|
result = hugepage_vma_revalidate(mm, address, &vma); |
|
if (result) { |
|
mmap_read_unlock(mm); |
|
goto out_nolock; |
|
} |
|
|
|
pmd = mm_find_pmd(mm, address); |
|
if (!pmd) { |
|
result = SCAN_PMD_NULL; |
|
mmap_read_unlock(mm); |
|
goto out_nolock; |
|
} |
|
|
|
/* |
|
* __collapse_huge_page_swapin will return with mmap_lock released |
|
* when it fails. So we jump out_nolock directly in that case. |
|
* Continuing to collapse causes inconsistency. |
|
*/ |
|
if (unmapped && !__collapse_huge_page_swapin(mm, vma, address, |
|
pmd, referenced)) { |
|
goto out_nolock; |
|
} |
|
|
|
mmap_read_unlock(mm); |
|
/* |
|
* Prevent all access to pagetables with the exception of |
|
* gup_fast later handled by the ptep_clear_flush and the VM |
|
* handled by the anon_vma lock + PG_lock. |
|
*/ |
|
mmap_write_lock(mm); |
|
result = hugepage_vma_revalidate(mm, address, &vma); |
|
if (result) |
|
goto out_up_write; |
|
/* check if the pmd is still valid */ |
|
if (mm_find_pmd(mm, address) != pmd) |
|
goto out_up_write; |
|
|
|
anon_vma_lock_write(vma->anon_vma); |
|
|
|
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, |
|
address, address + HPAGE_PMD_SIZE); |
|
mmu_notifier_invalidate_range_start(&range); |
|
|
|
pte = pte_offset_map(pmd, address); |
|
pte_ptl = pte_lockptr(mm, pmd); |
|
|
|
pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ |
|
/* |
|
* After this gup_fast can't run anymore. This also removes |
|
* any huge TLB entry from the CPU so we won't allow |
|
* huge and small TLB entries for the same virtual address |
|
* to avoid the risk of CPU bugs in that area. |
|
*/ |
|
_pmd = pmdp_collapse_flush(vma, address, pmd); |
|
spin_unlock(pmd_ptl); |
|
mmu_notifier_invalidate_range_end(&range); |
|
|
|
spin_lock(pte_ptl); |
|
isolated = __collapse_huge_page_isolate(vma, address, pte, |
|
&compound_pagelist); |
|
spin_unlock(pte_ptl); |
|
|
|
if (unlikely(!isolated)) { |
|
pte_unmap(pte); |
|
spin_lock(pmd_ptl); |
|
BUG_ON(!pmd_none(*pmd)); |
|
/* |
|
* We can only use set_pmd_at when establishing |
|
* hugepmds and never for establishing regular pmds that |
|
* points to regular pagetables. Use pmd_populate for that |
|
*/ |
|
pmd_populate(mm, pmd, pmd_pgtable(_pmd)); |
|
spin_unlock(pmd_ptl); |
|
anon_vma_unlock_write(vma->anon_vma); |
|
result = SCAN_FAIL; |
|
goto out_up_write; |
|
} |
|
|
|
/* |
|
* All pages are isolated and locked so anon_vma rmap |
|
* can't run anymore. |
|
*/ |
|
anon_vma_unlock_write(vma->anon_vma); |
|
|
|
__collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl, |
|
&compound_pagelist); |
|
pte_unmap(pte); |
|
/* |
|
* spin_lock() below is not the equivalent of smp_wmb(), but |
|
* the smp_wmb() inside __SetPageUptodate() can be reused to |
|
* avoid the copy_huge_page writes to become visible after |
|
* the set_pmd_at() write. |
|
*/ |
|
__SetPageUptodate(new_page); |
|
pgtable = pmd_pgtable(_pmd); |
|
|
|
_pmd = mk_huge_pmd(new_page, vma->vm_page_prot); |
|
_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); |
|
|
|
spin_lock(pmd_ptl); |
|
BUG_ON(!pmd_none(*pmd)); |
|
page_add_new_anon_rmap(new_page, vma, address); |
|
lru_cache_add_inactive_or_unevictable(new_page, vma); |
|
pgtable_trans_huge_deposit(mm, pmd, pgtable); |
|
set_pmd_at(mm, address, pmd, _pmd); |
|
update_mmu_cache_pmd(vma, address, pmd); |
|
spin_unlock(pmd_ptl); |
|
|
|
*hpage = NULL; |
|
|
|
khugepaged_pages_collapsed++; |
|
result = SCAN_SUCCEED; |
|
out_up_write: |
|
mmap_write_unlock(mm); |
|
out_nolock: |
|
if (!IS_ERR_OR_NULL(*hpage)) |
|
mem_cgroup_uncharge(page_folio(*hpage)); |
|
trace_mm_collapse_huge_page(mm, isolated, result); |
|
return; |
|
} |
|
|
|
static int khugepaged_scan_pmd(struct mm_struct *mm, |
|
struct vm_area_struct *vma, |
|
unsigned long address, |
|
struct page **hpage) |
|
{ |
|
pmd_t *pmd; |
|
pte_t *pte, *_pte; |
|
int ret = 0, result = 0, referenced = 0; |
|
int none_or_zero = 0, shared = 0; |
|
struct page *page = NULL; |
|
unsigned long _address; |
|
spinlock_t *ptl; |
|
int node = NUMA_NO_NODE, unmapped = 0; |
|
bool writable = false; |
|
|
|
VM_BUG_ON(address & ~HPAGE_PMD_MASK); |
|
|
|
pmd = mm_find_pmd(mm, address); |
|
if (!pmd) { |
|
result = SCAN_PMD_NULL; |
|
goto out; |
|
} |
|
|
|
memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); |
|
pte = pte_offset_map_lock(mm, pmd, address, &ptl); |
|
for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR; |
|
_pte++, _address += PAGE_SIZE) { |
|
pte_t pteval = *_pte; |
|
if (is_swap_pte(pteval)) { |
|
if (++unmapped <= khugepaged_max_ptes_swap) { |
|
/* |
|
* Always be strict with uffd-wp |
|
* enabled swap entries. Please see |
|
* comment below for pte_uffd_wp(). |
|
*/ |
|
if (pte_swp_uffd_wp(pteval)) { |
|
result = SCAN_PTE_UFFD_WP; |
|
goto out_unmap; |
|
} |
|
continue; |
|
} else { |
|
result = SCAN_EXCEED_SWAP_PTE; |
|
count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); |
|
goto out_unmap; |
|
} |
|
} |
|
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { |
|
if (!userfaultfd_armed(vma) && |
|
++none_or_zero <= khugepaged_max_ptes_none) { |
|
continue; |
|
} else { |
|
result = SCAN_EXCEED_NONE_PTE; |
|
count_vm_event(THP_SCAN_EXCEED_NONE_PTE); |
|
goto out_unmap; |
|
} |
|
} |
|
if (pte_uffd_wp(pteval)) { |
|
/* |
|
* Don't collapse the page if any of the small |
|
* PTEs are armed with uffd write protection. |
|
* Here we can also mark the new huge pmd as |
|
* write protected if any of the small ones is |
|
* marked but that could bring unknown |
|
* userfault messages that falls outside of |
|
* the registered range. So, just be simple. |
|
*/ |
|
result = SCAN_PTE_UFFD_WP; |
|
goto out_unmap; |
|
} |
|
if (pte_write(pteval)) |
|
writable = true; |
|
|
|
page = vm_normal_page(vma, _address, pteval); |
|
if (unlikely(!page) || unlikely(is_zone_device_page(page))) { |
|
result = SCAN_PAGE_NULL; |
|
goto out_unmap; |
|
} |
|
|
|
if (page_mapcount(page) > 1 && |
|
++shared > khugepaged_max_ptes_shared) { |
|
result = SCAN_EXCEED_SHARED_PTE; |
|
count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); |
|
goto out_unmap; |
|
} |
|
|
|
page = compound_head(page); |
|
|
|
/* |
|
* Record which node the original page is from and save this |
|
* information to khugepaged_node_load[]. |
|
* Khugepaged will allocate hugepage from the node has the max |
|
* hit record. |
|
*/ |
|
node = page_to_nid(page); |
|
if (khugepaged_scan_abort(node)) { |
|
result = SCAN_SCAN_ABORT; |
|
goto out_unmap; |
|
} |
|
khugepaged_node_load[node]++; |
|
if (!PageLRU(page)) { |
|
result = SCAN_PAGE_LRU; |
|
goto out_unmap; |
|
} |
|
if (PageLocked(page)) { |
|
result = SCAN_PAGE_LOCK; |
|
goto out_unmap; |
|
} |
|
if (!PageAnon(page)) { |
|
result = SCAN_PAGE_ANON; |
|
goto out_unmap; |
|
} |
|
|
|
/* |
|
* Check if the page has any GUP (or other external) pins. |
|
* |
|
* Here the check is racy it may see total_mapcount > refcount |
|
* in some cases. |
|
* For example, one process with one forked child process. |
|
* The parent has the PMD split due to MADV_DONTNEED, then |
|
* the child is trying unmap the whole PMD, but khugepaged |
|
* may be scanning the parent between the child has |
|
* PageDoubleMap flag cleared and dec the mapcount. So |
|
* khugepaged may see total_mapcount > refcount. |
|
* |
|
* But such case is ephemeral we could always retry collapse |
|
* later. However it may report false positive if the page |
|
* has excessive GUP pins (i.e. 512). Anyway the same check |
|
* will be done again later the risk seems low. |
|
*/ |
|
if (!is_refcount_suitable(page)) { |
|
result = SCAN_PAGE_COUNT; |
|
goto out_unmap; |
|
} |
|
if (pte_young(pteval) || |
|
page_is_young(page) || PageReferenced(page) || |
|
mmu_notifier_test_young(vma->vm_mm, address)) |
|
referenced++; |
|
} |
|
if (!writable) { |
|
result = SCAN_PAGE_RO; |
|
} else if (!referenced || (unmapped && referenced < HPAGE_PMD_NR/2)) { |
|
result = SCAN_LACK_REFERENCED_PAGE; |
|
} else { |
|
result = SCAN_SUCCEED; |
|
ret = 1; |
|
} |
|
out_unmap: |
|
pte_unmap_unlock(pte, ptl); |
|
if (ret) { |
|
node = khugepaged_find_target_node(); |
|
/* collapse_huge_page will return with the mmap_lock released */ |
|
collapse_huge_page(mm, address, hpage, node, |
|
referenced, unmapped); |
|
} |
|
out: |
|
trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, |
|
none_or_zero, result, unmapped); |
|
return ret; |
|
} |
|
|
|
static void collect_mm_slot(struct mm_slot *mm_slot) |
|
{ |
|
struct mm_struct *mm = mm_slot->mm; |
|
|
|
lockdep_assert_held(&khugepaged_mm_lock); |
|
|
|
if (khugepaged_test_exit(mm)) { |
|
/* free mm_slot */ |
|
hash_del(&mm_slot->hash); |
|
list_del(&mm_slot->mm_node); |
|
|
|
/* |
|
* Not strictly needed because the mm exited already. |
|
* |
|
* clear_bit(MMF_VM_HUGEPAGE, &mm->flags); |
|
*/ |
|
|
|
/* khugepaged_mm_lock actually not necessary for the below */ |
|
free_mm_slot(mm_slot); |
|
mmdrop(mm); |
|
} |
|
} |
|
|
|
#ifdef CONFIG_SHMEM |
|
/* |
|
* Notify khugepaged that given addr of the mm is pte-mapped THP. Then |
|
* khugepaged should try to collapse the page table. |
|
*/ |
|
static void khugepaged_add_pte_mapped_thp(struct mm_struct *mm, |
|
unsigned long addr) |
|
{ |
|
struct mm_slot *mm_slot; |
|
|
|
VM_BUG_ON(addr & ~HPAGE_PMD_MASK); |
|
|
|
spin_lock(&khugepaged_mm_lock); |
|
mm_slot = get_mm_slot(mm); |
|
if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP)) |
|
mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr; |
|
spin_unlock(&khugepaged_mm_lock); |
|
} |
|
|
|
static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *vma, |
|
unsigned long addr, pmd_t *pmdp) |
|
{ |
|
spinlock_t *ptl; |
|
pmd_t pmd; |
|
|
|
mmap_assert_write_locked(mm); |
|
ptl = pmd_lock(vma->vm_mm, pmdp); |
|
pmd = pmdp_collapse_flush(vma, addr, pmdp); |
|
spin_unlock(ptl); |
|
mm_dec_nr_ptes(mm); |
|
page_table_check_pte_clear_range(mm, addr, pmd); |
|
pte_free(mm, pmd_pgtable(pmd)); |
|
} |
|
|
|
/** |
|
* collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at |
|
* address haddr. |
|
* |
|
* @mm: process address space where collapse happens |
|
* @addr: THP collapse address |
|
* |
|
* This function checks whether all the PTEs in the PMD are pointing to the |
|
* right THP. If so, retract the page table so the THP can refault in with |
|
* as pmd-mapped. |
|
*/ |
|
void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) |
|
{ |
|
unsigned long haddr = addr & HPAGE_PMD_MASK; |
|
struct vm_area_struct *vma = find_vma(mm, haddr); |
|
struct page *hpage; |
|
pte_t *start_pte, *pte; |
|
pmd_t *pmd; |
|
spinlock_t *ptl; |
|
int count = 0; |
|
int i; |
|
|
|
if (!vma || !vma->vm_file || |
|
!range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE)) |
|
return; |
|
|
|
/* |
|
* This vm_flags may not have VM_HUGEPAGE if the page was not |
|
* collapsed by this mm. But we can still collapse if the page is |
|
* the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check() |
|
* will not fail the vma for missing VM_HUGEPAGE |
|
*/ |
|
if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE, false, false)) |
|
return; |
|
|
|
/* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */ |
|
if (userfaultfd_wp(vma)) |
|
return; |
|
|
|
hpage = find_lock_page(vma->vm_file->f_mapping, |
|
linear_page_index(vma, haddr)); |
|
if (!hpage) |
|
return; |
|
|
|
if (!PageHead(hpage)) |
|
goto drop_hpage; |
|
|
|
pmd = mm_find_pmd(mm, haddr); |
|
if (!pmd) |
|
goto drop_hpage; |
|
|
|
start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl); |
|
|
|
/* step 1: check all mapped PTEs are to the right huge page */ |
|
for (i = 0, addr = haddr, pte = start_pte; |
|
i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { |
|
struct page *page; |
|
|
|
/* empty pte, skip */ |
|
if (pte_none(*pte)) |
|
continue; |
|
|
|
/* page swapped out, abort */ |
|
if (!pte_present(*pte)) |
|
goto abort; |
|
|
|
page = vm_normal_page(vma, addr, *pte); |
|
if (WARN_ON_ONCE(page && is_zone_device_page(page))) |
|
page = NULL; |
|
/* |
|
* Note that uprobe, debugger, or MAP_PRIVATE may change the |
|
* page table, but the new page will not be a subpage of hpage. |
|
*/ |
|
if (hpage + i != page) |
|
goto abort; |
|
count++; |
|
} |
|
|
|
/* step 2: adjust rmap */ |
|
for (i = 0, addr = haddr, pte = start_pte; |
|
i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { |
|
struct page *page; |
|
|
|
if (pte_none(*pte)) |
|
continue; |
|
page = vm_normal_page(vma, addr, *pte); |
|
if (WARN_ON_ONCE(page && is_zone_device_page(page))) |
|
goto abort; |
|
page_remove_rmap(page, vma, false); |
|
} |
|
|
|
pte_unmap_unlock(start_pte, ptl); |
|
|
|
/* step 3: set proper refcount and mm_counters. */ |
|
if (count) { |
|
page_ref_sub(hpage, count); |
|
add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -count); |
|
} |
|
|
|
/* step 4: collapse pmd */ |
|
collapse_and_free_pmd(mm, vma, haddr, pmd); |
|
drop_hpage: |
|
unlock_page(hpage); |
|
put_page(hpage); |
|
return; |
|
|
|
abort: |
|
pte_unmap_unlock(start_pte, ptl); |
|
goto drop_hpage; |
|
} |
|
|
|
static void khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot) |
|
{ |
|
struct mm_struct *mm = mm_slot->mm; |
|
int i; |
|
|
|
if (likely(mm_slot->nr_pte_mapped_thp == 0)) |
|
return; |
|
|
|
if (!mmap_write_trylock(mm)) |
|
return; |
|
|
|
if (unlikely(khugepaged_test_exit(mm))) |
|
goto out; |
|
|
|
for (i = 0; i < mm_slot->nr_pte_mapped_thp; i++) |
|
collapse_pte_mapped_thp(mm, mm_slot->pte_mapped_thp[i]); |
|
|
|
out: |
|
mm_slot->nr_pte_mapped_thp = 0; |
|
mmap_write_unlock(mm); |
|
} |
|
|
|
static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) |
|
{ |
|
struct vm_area_struct *vma; |
|
struct mm_struct *mm; |
|
unsigned long addr; |
|
pmd_t *pmd; |
|
|
|
i_mmap_lock_write(mapping); |
|
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { |
|
/* |
|
* Check vma->anon_vma to exclude MAP_PRIVATE mappings that |
|
* got written to. These VMAs are likely not worth investing |
|
* mmap_write_lock(mm) as PMD-mapping is likely to be split |
|
* later. |
|
* |
|
* Note that vma->anon_vma check is racy: it can be set up after |
|
* the check but before we took mmap_lock by the fault path. |
|
* But page lock would prevent establishing any new ptes of the |
|
* page, so we are safe. |
|
* |
|
* An alternative would be drop the check, but check that page |
|
* table is clear before calling pmdp_collapse_flush() under |
|
* ptl. It has higher chance to recover THP for the VMA, but |
|
* has higher cost too. |
|
*/ |
|
if (vma->anon_vma) |
|
continue; |
|
addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
|
if (addr & ~HPAGE_PMD_MASK) |
|
continue; |
|
if (vma->vm_end < addr + HPAGE_PMD_SIZE) |
|
continue; |
|
mm = vma->vm_mm; |
|
pmd = mm_find_pmd(mm, addr); |
|
if (!pmd) |
|
continue; |
|
/* |
|
* We need exclusive mmap_lock to retract page table. |
|
* |
|
* We use trylock due to lock inversion: we need to acquire |
|
* mmap_lock while holding page lock. Fault path does it in |
|
* reverse order. Trylock is a way to avoid deadlock. |
|
*/ |
|
if (mmap_write_trylock(mm)) { |
|
/* |
|
* When a vma is registered with uffd-wp, we can't |
|
* recycle the pmd pgtable because there can be pte |
|
* markers installed. Skip it only, so the rest mm/vma |
|
* can still have the same file mapped hugely, however |
|
* it'll always mapped in small page size for uffd-wp |
|
* registered ranges. |
|
*/ |
|
if (!khugepaged_test_exit(mm) && !userfaultfd_wp(vma)) |
|
collapse_and_free_pmd(mm, vma, addr, pmd); |
|
mmap_write_unlock(mm); |
|
} else { |
|
/* Try again later */ |
|
khugepaged_add_pte_mapped_thp(mm, addr); |
|
} |
|
} |
|
i_mmap_unlock_write(mapping); |
|
} |
|
|
|
/** |
|
* collapse_file - collapse filemap/tmpfs/shmem pages into huge one. |
|
* |
|
* @mm: process address space where collapse happens |
|
* @file: file that collapse on |
|
* @start: collapse start address |
|
* @hpage: new allocated huge page for collapse |
|
* @node: appointed node the new huge page allocate from |
|
* |
|
* Basic scheme is simple, details are more complex: |
|
* - allocate and lock a new huge page; |
|
* - scan page cache replacing old pages with the new one |
|
* + swap/gup in pages if necessary; |
|
* + fill in gaps; |
|
* + keep old pages around in case rollback is required; |
|
* - if replacing succeeds: |
|
* + copy data over; |
|
* + free old pages; |
|
* + unlock huge page; |
|
* - if replacing failed; |
|
* + put all pages back and unfreeze them; |
|
* + restore gaps in the page cache; |
|
* + unlock and free huge page; |
|
*/ |
|
static void collapse_file(struct mm_struct *mm, |
|
struct file *file, pgoff_t start, |
|
struct page **hpage, int node) |
|
{ |
|
struct address_space *mapping = file->f_mapping; |
|
gfp_t gfp; |
|
struct page *new_page; |
|
pgoff_t index, end = start + HPAGE_PMD_NR; |
|
LIST_HEAD(pagelist); |
|
XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); |
|
int nr_none = 0, result = SCAN_SUCCEED; |
|
bool is_shmem = shmem_file(file); |
|
int nr; |
|
|
|
VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); |
|
VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); |
|
|
|
/* Only allocate from the target node */ |
|
gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
|
|
|
new_page = khugepaged_alloc_page(hpage, gfp, node); |
|
if (!new_page) { |
|
result = SCAN_ALLOC_HUGE_PAGE_FAIL; |
|
goto out; |
|
} |
|
|
|
if (unlikely(mem_cgroup_charge(page_folio(new_page), mm, gfp))) { |
|
result = SCAN_CGROUP_CHARGE_FAIL; |
|
goto out; |
|
} |
|
count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC); |
|
|
|
/* |
|
* Ensure we have slots for all the pages in the range. This is |
|
* almost certainly a no-op because most of the pages must be present |
|
*/ |
|
do { |
|
xas_lock_irq(&xas); |
|
xas_create_range(&xas); |
|
if (!xas_error(&xas)) |
|
break; |
|
xas_unlock_irq(&xas); |
|
if (!xas_nomem(&xas, GFP_KERNEL)) { |
|
result = SCAN_FAIL; |
|
goto out; |
|
} |
|
} while (1); |
|
|
|
__SetPageLocked(new_page); |
|
if (is_shmem) |
|
__SetPageSwapBacked(new_page); |
|
new_page->index = start; |
|
new_page->mapping = mapping; |
|
|
|
/* |
|
* At this point the new_page is locked and not up-to-date. |
|
* It's safe to insert it into the page cache, because nobody would |
|
* be able to map it or use it in another way until we unlock it. |
|
*/ |
|
|
|
xas_set(&xas, start); |
|
for (index = start; index < end; index++) { |
|
struct page *page = xas_next(&xas); |
|
|
|
VM_BUG_ON(index != xas.xa_index); |
|
if (is_shmem) { |
|
if (!page) { |
|
/* |
|
* Stop if extent has been truncated or |
|
* hole-punched, and is now completely |
|
* empty. |
|
*/ |
|
if (index == start) { |
|
if (!xas_next_entry(&xas, end - 1)) { |
|
result = SCAN_TRUNCATED; |
|
goto xa_locked; |
|
} |
|
xas_set(&xas, index); |
|
} |
|
if (!shmem_charge(mapping->host, 1)) { |
|
result = SCAN_FAIL; |
|
goto xa_locked; |
|
} |
|
xas_store(&xas, new_page); |
|
nr_none++; |
|
continue; |
|
} |
|
|
|
if (xa_is_value(page) || !PageUptodate(page)) { |
|
xas_unlock_irq(&xas); |
|
/* swap in or instantiate fallocated page */ |
|
if (shmem_getpage(mapping->host, index, &page, |
|
SGP_NOALLOC)) { |
|
result = SCAN_FAIL; |
|
goto xa_unlocked; |
|
} |
|
} else if (trylock_page(page)) { |
|
get_page(page); |
|
xas_unlock_irq(&xas); |
|
} else { |
|
result = SCAN_PAGE_LOCK; |
|
goto xa_locked; |
|
} |
|
} else { /* !is_shmem */ |
|
if (!page || xa_is_value(page)) { |
|
xas_unlock_irq(&xas); |
|
page_cache_sync_readahead(mapping, &file->f_ra, |
|
file, index, |
|
end - index); |
|
/* drain pagevecs to help isolate_lru_page() */ |
|
lru_add_drain(); |
|
page = find_lock_page(mapping, index); |
|
if (unlikely(page == NULL)) { |
|
result = SCAN_FAIL; |
|
goto xa_unlocked; |
|
} |
|
} else if (PageDirty(page)) { |
|
/* |
|
* khugepaged only works on read-only fd, |
|
* so this page is dirty because it hasn't |
|
* been flushed since first write. There |
|
* won't be new dirty pages. |
|
* |
|
* Trigger async flush here and hope the |
|
* writeback is done when khugepaged |
|
* revisits this page. |
|
* |
|
* This is a one-off situation. We are not |
|
* forcing writeback in loop. |
|
*/ |
|
xas_unlock_irq(&xas); |
|
filemap_flush(mapping); |
|
result = SCAN_FAIL; |
|
goto xa_unlocked; |
|
} else if (PageWriteback(page)) { |
|
xas_unlock_irq(&xas); |
|
result = SCAN_FAIL; |
|
goto xa_unlocked; |
|
} else if (trylock_page(page)) { |
|
get_page(page); |
|
xas_unlock_irq(&xas); |
|
} else { |
|
result = SCAN_PAGE_LOCK; |
|
goto xa_locked; |
|
} |
|
} |
|
|
|
/* |
|
* The page must be locked, so we can drop the i_pages lock |
|
* without racing with truncate. |
|
*/ |
|
VM_BUG_ON_PAGE(!PageLocked(page), page); |
|
|
|
/* make sure the page is up to date */ |
|
if (unlikely(!PageUptodate(page))) { |
|
result = SCAN_FAIL; |
|
goto out_unlock; |
|
} |
|
|
|
/* |
|
* If file was truncated then extended, or hole-punched, before |
|
* we locked the first page, then a THP might be there already. |
|
*/ |
|
if (PageTransCompound(page)) { |
|
result = SCAN_PAGE_COMPOUND; |
|
goto out_unlock; |
|
} |
|
|
|
if (page_mapping(page) != mapping) { |
|
result = SCAN_TRUNCATED; |
|
goto out_unlock; |
|
} |
|
|
|
if (!is_shmem && (PageDirty(page) || |
|
PageWriteback(page))) { |
|
/* |
|
* khugepaged only works on read-only fd, so this |
|
* page is dirty because it hasn't been flushed |
|
* since first write. |
|
*/ |
|
result = SCAN_FAIL; |
|
goto out_unlock; |
|
} |
|
|
|
if (isolate_lru_page(page)) { |
|
result = SCAN_DEL_PAGE_LRU; |
|
goto out_unlock; |
|
} |
|
|
|
if (page_has_private(page) && |
|
!try_to_release_page(page, GFP_KERNEL)) { |
|
result = SCAN_PAGE_HAS_PRIVATE; |
|
putback_lru_page(page); |
|
goto out_unlock; |
|
} |
|
|
|
if (page_mapped(page)) |
|
try_to_unmap(page_folio(page), |
|
TTU_IGNORE_MLOCK | TTU_BATCH_FLUSH); |
|
|
|
xas_lock_irq(&xas); |
|
xas_set(&xas, index); |
|
|
|
VM_BUG_ON_PAGE(page != xas_load(&xas), page); |
|
|
|
/* |
|
* The page is expected to have page_count() == 3: |
|
* - we hold a pin on it; |
|
* - one reference from page cache; |
|
* - one from isolate_lru_page; |
|
*/ |
|
if (!page_ref_freeze(page, 3)) { |
|
result = SCAN_PAGE_COUNT; |
|
xas_unlock_irq(&xas); |
|
putback_lru_page(page); |
|
goto out_unlock; |
|
} |
|
|
|
/* |
|
* Add the page to the list to be able to undo the collapse if |
|
* something go wrong. |
|
*/ |
|
list_add_tail(&page->lru, &pagelist); |
|
|
|
/* Finally, replace with the new page. */ |
|
xas_store(&xas, new_page); |
|
continue; |
|
out_unlock: |
|
unlock_page(page); |
|
put_page(page); |
|
goto xa_unlocked; |
|
} |
|
nr = thp_nr_pages(new_page); |
|
|
|
if (is_shmem) |
|
__mod_lruvec_page_state(new_page, NR_SHMEM_THPS, nr); |
|
else { |
|
__mod_lruvec_page_state(new_page, NR_FILE_THPS, nr); |
|
filemap_nr_thps_inc(mapping); |
|
/* |
|
* Paired with smp_mb() in do_dentry_open() to ensure |
|
* i_writecount is up to date and the update to nr_thps is |
|
* visible. Ensures the page cache will be truncated if the |
|
* file is opened writable. |
|
*/ |
|
smp_mb(); |
|
if (inode_is_open_for_write(mapping->host)) { |
|
result = SCAN_FAIL; |
|
__mod_lruvec_page_state(new_page, NR_FILE_THPS, -nr); |
|
filemap_nr_thps_dec(mapping); |
|
goto xa_locked; |
|
} |
|
} |
|
|
|
if (nr_none) { |
|
__mod_lruvec_page_state(new_page, NR_FILE_PAGES, nr_none); |
|
/* nr_none is always 0 for non-shmem. */ |
|
__mod_lruvec_page_state(new_page, NR_SHMEM, nr_none); |
|
} |
|
|
|
/* Join all the small entries into a single multi-index entry */ |
|
xas_set_order(&xas, start, HPAGE_PMD_ORDER); |
|
xas_store(&xas, new_page); |
|
xa_locked: |
|
xas_unlock_irq(&xas); |
|
xa_unlocked: |
|
|
|
/* |
|
* If collapse is successful, flush must be done now before copying. |
|
* If collapse is unsuccessful, does flush actually need to be done? |
|
* Do it anyway, to clear the state. |
|
*/ |
|
try_to_unmap_flush(); |
|
|
|
if (result == SCAN_SUCCEED) { |
|
struct page *page, *tmp; |
|
|
|
/* |
|
* Replacing old pages with new one has succeeded, now we |
|
* need to copy the content and free the old pages. |
|
*/ |
|
index = start; |
|
list_for_each_entry_safe(page, tmp, &pagelist, lru) { |
|
while (index < page->index) { |
|
clear_highpage(new_page + (index % HPAGE_PMD_NR)); |
|
index++; |
|
} |
|
copy_highpage(new_page + (page->index % HPAGE_PMD_NR), |
|
page); |
|
list_del(&page->lru); |
|
page->mapping = NULL; |
|
page_ref_unfreeze(page, 1); |
|
ClearPageActive(page); |
|
ClearPageUnevictable(page); |
|
unlock_page(page); |
|
put_page(page); |
|
index++; |
|
} |
|
while (index < end) { |
|
clear_highpage(new_page + (index % HPAGE_PMD_NR)); |
|
index++; |
|
} |
|
|
|
SetPageUptodate(new_page); |
|
page_ref_add(new_page, HPAGE_PMD_NR - 1); |
|
if (is_shmem) |
|
set_page_dirty(new_page); |
|
lru_cache_add(new_page); |
|
|
|
/* |
|
* Remove pte page tables, so we can re-fault the page as huge. |
|
*/ |
|
retract_page_tables(mapping, start); |
|
*hpage = NULL; |
|
|
|
khugepaged_pages_collapsed++; |
|
} else { |
|
struct page *page; |
|
|
|
/* Something went wrong: roll back page cache changes */ |
|
xas_lock_irq(&xas); |
|
if (nr_none) { |
|
mapping->nrpages -= nr_none; |
|
shmem_uncharge(mapping->host, nr_none); |
|
} |
|
|
|
xas_set(&xas, start); |
|
xas_for_each(&xas, page, end - 1) { |
|
page = list_first_entry_or_null(&pagelist, |
|
struct page, lru); |
|
if (!page || xas.xa_index < page->index) { |
|
if (!nr_none) |
|
break; |
|
nr_none--; |
|
/* Put holes back where they were */ |
|
xas_store(&xas, NULL); |
|
continue; |
|
} |
|
|
|
VM_BUG_ON_PAGE(page->index != xas.xa_index, page); |
|
|
|
/* Unfreeze the page. */ |
|
list_del(&page->lru); |
|
page_ref_unfreeze(page, 2); |
|
xas_store(&xas, page); |
|
xas_pause(&xas); |
|
xas_unlock_irq(&xas); |
|
unlock_page(page); |
|
putback_lru_page(page); |
|
xas_lock_irq(&xas); |
|
} |
|
VM_BUG_ON(nr_none); |
|
xas_unlock_irq(&xas); |
|
|
|
new_page->mapping = NULL; |
|
} |
|
|
|
unlock_page(new_page); |
|
out: |
|
VM_BUG_ON(!list_empty(&pagelist)); |
|
if (!IS_ERR_OR_NULL(*hpage)) |
|
mem_cgroup_uncharge(page_folio(*hpage)); |
|
/* TODO: tracepoints */ |
|
} |
|
|
|
static void khugepaged_scan_file(struct mm_struct *mm, |
|
struct file *file, pgoff_t start, struct page **hpage) |
|
{ |
|
struct page *page = NULL; |
|
struct address_space *mapping = file->f_mapping; |
|
XA_STATE(xas, &mapping->i_pages, start); |
|
int present, swap; |
|
int node = NUMA_NO_NODE; |
|
int result = SCAN_SUCCEED; |
|
|
|
present = 0; |
|
swap = 0; |
|
memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); |
|
rcu_read_lock(); |
|
xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) { |
|
if (xas_retry(&xas, page)) |
|
continue; |
|
|
|
if (xa_is_value(page)) { |
|
if (++swap > khugepaged_max_ptes_swap) { |
|
result = SCAN_EXCEED_SWAP_PTE; |
|
count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); |
|
break; |
|
} |
|
continue; |
|
} |
|
|
|
/* |
|
* XXX: khugepaged should compact smaller compound pages |
|
* into a PMD sized page |
|
*/ |
|
if (PageTransCompound(page)) { |
|
result = SCAN_PAGE_COMPOUND; |
|
break; |
|
} |
|
|
|
node = page_to_nid(page); |
|
if (khugepaged_scan_abort(node)) { |
|
result = SCAN_SCAN_ABORT; |
|
break; |
|
} |
|
khugepaged_node_load[node]++; |
|
|
|
if (!PageLRU(page)) { |
|
result = SCAN_PAGE_LRU; |
|
break; |
|
} |
|
|
|
if (page_count(page) != |
|
1 + page_mapcount(page) + page_has_private(page)) { |
|
result = SCAN_PAGE_COUNT; |
|
break; |
|
} |
|
|
|
/* |
|
* We probably should check if the page is referenced here, but |
|
* nobody would transfer pte_young() to PageReferenced() for us. |
|
* And rmap walk here is just too costly... |
|
*/ |
|
|
|
present++; |
|
|
|
if (need_resched()) { |
|
xas_pause(&xas); |
|
cond_resched_rcu(); |
|
} |
|
} |
|
rcu_read_unlock(); |
|
|
|
if (result == SCAN_SUCCEED) { |
|
if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { |
|
result = SCAN_EXCEED_NONE_PTE; |
|
count_vm_event(THP_SCAN_EXCEED_NONE_PTE); |
|
} else { |
|
node = khugepaged_find_target_node(); |
|
collapse_file(mm, file, start, hpage, node); |
|
} |
|
} |
|
|
|
/* TODO: tracepoints */ |
|
} |
|
#else |
|
static void khugepaged_scan_file(struct mm_struct *mm, |
|
struct file *file, pgoff_t start, struct page **hpage) |
|
{ |
|
BUILD_BUG(); |
|
} |
|
|
|
static void khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot) |
|
{ |
|
} |
|
#endif |
|
|
|
static unsigned int khugepaged_scan_mm_slot(unsigned int pages, |
|
struct page **hpage) |
|
__releases(&khugepaged_mm_lock) |
|
__acquires(&khugepaged_mm_lock) |
|
{ |
|
struct mm_slot *mm_slot; |
|
struct mm_struct *mm; |
|
struct vm_area_struct *vma; |
|
int progress = 0; |
|
|
|
VM_BUG_ON(!pages); |
|
lockdep_assert_held(&khugepaged_mm_lock); |
|
|
|
if (khugepaged_scan.mm_slot) |
|
mm_slot = khugepaged_scan.mm_slot; |
|
else { |
|
mm_slot = list_entry(khugepaged_scan.mm_head.next, |
|
struct mm_slot, mm_node); |
|
khugepaged_scan.address = 0; |
|
khugepaged_scan.mm_slot = mm_slot; |
|
} |
|
spin_unlock(&khugepaged_mm_lock); |
|
khugepaged_collapse_pte_mapped_thps(mm_slot); |
|
|
|
mm = mm_slot->mm; |
|
/* |
|
* Don't wait for semaphore (to avoid long wait times). Just move to |
|
* the next mm on the list. |
|
*/ |
|
vma = NULL; |
|
if (unlikely(!mmap_read_trylock(mm))) |
|
goto breakouterloop_mmap_lock; |
|
if (likely(!khugepaged_test_exit(mm))) |
|
vma = find_vma(mm, khugepaged_scan.address); |
|
|
|
progress++; |
|
for (; vma; vma = vma->vm_next) { |
|
unsigned long hstart, hend; |
|
|
|
cond_resched(); |
|
if (unlikely(khugepaged_test_exit(mm))) { |
|
progress++; |
|
break; |
|
} |
|
if (!hugepage_vma_check(vma, vma->vm_flags, false, false)) { |
|
skip: |
|
progress++; |
|
continue; |
|
} |
|
hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE); |
|
hend = round_down(vma->vm_end, HPAGE_PMD_SIZE); |
|
if (khugepaged_scan.address > hend) |
|
goto skip; |
|
if (khugepaged_scan.address < hstart) |
|
khugepaged_scan.address = hstart; |
|
VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); |
|
|
|
while (khugepaged_scan.address < hend) { |
|
int ret; |
|
cond_resched(); |
|
if (unlikely(khugepaged_test_exit(mm))) |
|
goto breakouterloop; |
|
|
|
VM_BUG_ON(khugepaged_scan.address < hstart || |
|
khugepaged_scan.address + HPAGE_PMD_SIZE > |
|
hend); |
|
if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) { |
|
struct file *file = get_file(vma->vm_file); |
|
pgoff_t pgoff = linear_page_index(vma, |
|
khugepaged_scan.address); |
|
|
|
mmap_read_unlock(mm); |
|
ret = 1; |
|
khugepaged_scan_file(mm, file, pgoff, hpage); |
|
fput(file); |
|
} else { |
|
ret = khugepaged_scan_pmd(mm, vma, |
|
khugepaged_scan.address, |
|
hpage); |
|
} |
|
/* move to next address */ |
|
khugepaged_scan.address += HPAGE_PMD_SIZE; |
|
progress += HPAGE_PMD_NR; |
|
if (ret) |
|
/* we released mmap_lock so break loop */ |
|
goto breakouterloop_mmap_lock; |
|
if (progress >= pages) |
|
goto breakouterloop; |
|
} |
|
} |
|
breakouterloop: |
|
mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */ |
|
breakouterloop_mmap_lock: |
|
|
|
spin_lock(&khugepaged_mm_lock); |
|
VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); |
|
/* |
|
* Release the current mm_slot if this mm is about to die, or |
|
* if we scanned all vmas of this mm. |
|
*/ |
|
if (khugepaged_test_exit(mm) || !vma) { |
|
/* |
|
* Make sure that if mm_users is reaching zero while |
|
* khugepaged runs here, khugepaged_exit will find |
|
* mm_slot not pointing to the exiting mm. |
|
*/ |
|
if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { |
|
khugepaged_scan.mm_slot = list_entry( |
|
mm_slot->mm_node.next, |
|
struct mm_slot, mm_node); |
|
khugepaged_scan.address = 0; |
|
} else { |
|
khugepaged_scan.mm_slot = NULL; |
|
khugepaged_full_scans++; |
|
} |
|
|
|
collect_mm_slot(mm_slot); |
|
} |
|
|
|
return progress; |
|
} |
|
|
|
static int khugepaged_has_work(void) |
|
{ |
|
return !list_empty(&khugepaged_scan.mm_head) && |
|
hugepage_flags_enabled(); |
|
} |
|
|
|
static int khugepaged_wait_event(void) |
|
{ |
|
return !list_empty(&khugepaged_scan.mm_head) || |
|
kthread_should_stop(); |
|
} |
|
|
|
static void khugepaged_do_scan(void) |
|
{ |
|
struct page *hpage = NULL; |
|
unsigned int progress = 0, pass_through_head = 0; |
|
unsigned int pages = READ_ONCE(khugepaged_pages_to_scan); |
|
bool wait = true; |
|
|
|
lru_add_drain_all(); |
|
|
|
while (progress < pages) { |
|
if (!khugepaged_prealloc_page(&hpage, &wait)) |
|
break; |
|
|
|
cond_resched(); |
|
|
|
if (unlikely(kthread_should_stop() || try_to_freeze())) |
|
break; |
|
|
|
spin_lock(&khugepaged_mm_lock); |
|
if (!khugepaged_scan.mm_slot) |
|
pass_through_head++; |
|
if (khugepaged_has_work() && |
|
pass_through_head < 2) |
|
progress += khugepaged_scan_mm_slot(pages - progress, |
|
&hpage); |
|
else |
|
progress = pages; |
|
spin_unlock(&khugepaged_mm_lock); |
|
} |
|
|
|
if (!IS_ERR_OR_NULL(hpage)) |
|
put_page(hpage); |
|
} |
|
|
|
static bool khugepaged_should_wakeup(void) |
|
{ |
|
return kthread_should_stop() || |
|
time_after_eq(jiffies, khugepaged_sleep_expire); |
|
} |
|
|
|
static void khugepaged_wait_work(void) |
|
{ |
|
if (khugepaged_has_work()) { |
|
const unsigned long scan_sleep_jiffies = |
|
msecs_to_jiffies(khugepaged_scan_sleep_millisecs); |
|
|
|
if (!scan_sleep_jiffies) |
|
return; |
|
|
|
khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; |
|
wait_event_freezable_timeout(khugepaged_wait, |
|
khugepaged_should_wakeup(), |
|
scan_sleep_jiffies); |
|
return; |
|
} |
|
|
|
if (hugepage_flags_enabled()) |
|
wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); |
|
} |
|
|
|
static int khugepaged(void *none) |
|
{ |
|
struct mm_slot *mm_slot; |
|
|
|
set_freezable(); |
|
set_user_nice(current, MAX_NICE); |
|
|
|
while (!kthread_should_stop()) { |
|
khugepaged_do_scan(); |
|
khugepaged_wait_work(); |
|
} |
|
|
|
spin_lock(&khugepaged_mm_lock); |
|
mm_slot = khugepaged_scan.mm_slot; |
|
khugepaged_scan.mm_slot = NULL; |
|
if (mm_slot) |
|
collect_mm_slot(mm_slot); |
|
spin_unlock(&khugepaged_mm_lock); |
|
return 0; |
|
} |
|
|
|
static void set_recommended_min_free_kbytes(void) |
|
{ |
|
struct zone *zone; |
|
int nr_zones = 0; |
|
unsigned long recommended_min; |
|
|
|
if (!hugepage_flags_enabled()) { |
|
calculate_min_free_kbytes(); |
|
goto update_wmarks; |
|
} |
|
|
|
for_each_populated_zone(zone) { |
|
/* |
|
* We don't need to worry about fragmentation of |
|
* ZONE_MOVABLE since it only has movable pages. |
|
*/ |
|
if (zone_idx(zone) > gfp_zone(GFP_USER)) |
|
continue; |
|
|
|
nr_zones++; |
|
} |
|
|
|
/* Ensure 2 pageblocks are free to assist fragmentation avoidance */ |
|
recommended_min = pageblock_nr_pages * nr_zones * 2; |
|
|
|
/* |
|
* Make sure that on average at least two pageblocks are almost free |
|
* of another type, one for a migratetype to fall back to and a |
|
* second to avoid subsequent fallbacks of other types There are 3 |
|
* MIGRATE_TYPES we care about. |
|
*/ |
|
recommended_min += pageblock_nr_pages * nr_zones * |
|
MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; |
|
|
|
/* don't ever allow to reserve more than 5% of the lowmem */ |
|
recommended_min = min(recommended_min, |
|
(unsigned long) nr_free_buffer_pages() / 20); |
|
recommended_min <<= (PAGE_SHIFT-10); |
|
|
|
if (recommended_min > min_free_kbytes) { |
|
if (user_min_free_kbytes >= 0) |
|
pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", |
|
min_free_kbytes, recommended_min); |
|
|
|
min_free_kbytes = recommended_min; |
|
} |
|
|
|
update_wmarks: |
|
setup_per_zone_wmarks(); |
|
} |
|
|
|
int start_stop_khugepaged(void) |
|
{ |
|
int err = 0; |
|
|
|
mutex_lock(&khugepaged_mutex); |
|
if (hugepage_flags_enabled()) { |
|
if (!khugepaged_thread) |
|
khugepaged_thread = kthread_run(khugepaged, NULL, |
|
"khugepaged"); |
|
if (IS_ERR(khugepaged_thread)) { |
|
pr_err("khugepaged: kthread_run(khugepaged) failed\n"); |
|
err = PTR_ERR(khugepaged_thread); |
|
khugepaged_thread = NULL; |
|
goto fail; |
|
} |
|
|
|
if (!list_empty(&khugepaged_scan.mm_head)) |
|
wake_up_interruptible(&khugepaged_wait); |
|
} else if (khugepaged_thread) { |
|
kthread_stop(khugepaged_thread); |
|
khugepaged_thread = NULL; |
|
} |
|
set_recommended_min_free_kbytes(); |
|
fail: |
|
mutex_unlock(&khugepaged_mutex); |
|
return err; |
|
} |
|
|
|
void khugepaged_min_free_kbytes_update(void) |
|
{ |
|
mutex_lock(&khugepaged_mutex); |
|
if (hugepage_flags_enabled() && khugepaged_thread) |
|
set_recommended_min_free_kbytes(); |
|
mutex_unlock(&khugepaged_mutex); |
|
}
|
|
|