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1052 lines
28 KiB
1052 lines
28 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* The Kyber I/O scheduler. Controls latency by throttling queue depths using |
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* scalable techniques. |
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* |
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* Copyright (C) 2017 Facebook |
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*/ |
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|
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#include <linux/kernel.h> |
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#include <linux/blkdev.h> |
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#include <linux/blk-mq.h> |
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#include <linux/elevator.h> |
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#include <linux/module.h> |
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#include <linux/sbitmap.h> |
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|
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#include <trace/events/block.h> |
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|
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#include "blk.h" |
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#include "blk-mq.h" |
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#include "blk-mq-debugfs.h" |
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#include "blk-mq-sched.h" |
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#include "blk-mq-tag.h" |
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|
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#define CREATE_TRACE_POINTS |
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#include <trace/events/kyber.h> |
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|
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/* |
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* Scheduling domains: the device is divided into multiple domains based on the |
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* request type. |
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*/ |
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enum { |
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KYBER_READ, |
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KYBER_WRITE, |
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KYBER_DISCARD, |
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KYBER_OTHER, |
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KYBER_NUM_DOMAINS, |
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}; |
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|
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static const char *kyber_domain_names[] = { |
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[KYBER_READ] = "READ", |
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[KYBER_WRITE] = "WRITE", |
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[KYBER_DISCARD] = "DISCARD", |
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[KYBER_OTHER] = "OTHER", |
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}; |
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|
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enum { |
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/* |
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* In order to prevent starvation of synchronous requests by a flood of |
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* asynchronous requests, we reserve 25% of requests for synchronous |
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* operations. |
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*/ |
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KYBER_ASYNC_PERCENT = 75, |
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}; |
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|
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/* |
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* Maximum device-wide depth for each scheduling domain. |
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* |
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* Even for fast devices with lots of tags like NVMe, you can saturate the |
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* device with only a fraction of the maximum possible queue depth. So, we cap |
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* these to a reasonable value. |
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*/ |
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static const unsigned int kyber_depth[] = { |
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[KYBER_READ] = 256, |
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[KYBER_WRITE] = 128, |
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[KYBER_DISCARD] = 64, |
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[KYBER_OTHER] = 16, |
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}; |
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|
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/* |
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* Default latency targets for each scheduling domain. |
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*/ |
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static const u64 kyber_latency_targets[] = { |
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[KYBER_READ] = 2ULL * NSEC_PER_MSEC, |
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[KYBER_WRITE] = 10ULL * NSEC_PER_MSEC, |
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[KYBER_DISCARD] = 5ULL * NSEC_PER_SEC, |
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}; |
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|
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/* |
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* Batch size (number of requests we'll dispatch in a row) for each scheduling |
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* domain. |
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*/ |
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static const unsigned int kyber_batch_size[] = { |
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[KYBER_READ] = 16, |
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[KYBER_WRITE] = 8, |
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[KYBER_DISCARD] = 1, |
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[KYBER_OTHER] = 1, |
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}; |
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|
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/* |
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* Requests latencies are recorded in a histogram with buckets defined relative |
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* to the target latency: |
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* |
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* <= 1/4 * target latency |
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* <= 1/2 * target latency |
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* <= 3/4 * target latency |
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* <= target latency |
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* <= 1 1/4 * target latency |
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* <= 1 1/2 * target latency |
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* <= 1 3/4 * target latency |
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* > 1 3/4 * target latency |
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*/ |
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enum { |
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/* |
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* The width of the latency histogram buckets is |
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* 1 / (1 << KYBER_LATENCY_SHIFT) * target latency. |
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*/ |
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KYBER_LATENCY_SHIFT = 2, |
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/* |
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* The first (1 << KYBER_LATENCY_SHIFT) buckets are <= target latency, |
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* thus, "good". |
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*/ |
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KYBER_GOOD_BUCKETS = 1 << KYBER_LATENCY_SHIFT, |
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/* There are also (1 << KYBER_LATENCY_SHIFT) "bad" buckets. */ |
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KYBER_LATENCY_BUCKETS = 2 << KYBER_LATENCY_SHIFT, |
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}; |
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|
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/* |
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* We measure both the total latency and the I/O latency (i.e., latency after |
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* submitting to the device). |
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*/ |
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enum { |
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KYBER_TOTAL_LATENCY, |
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KYBER_IO_LATENCY, |
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}; |
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|
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static const char *kyber_latency_type_names[] = { |
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[KYBER_TOTAL_LATENCY] = "total", |
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[KYBER_IO_LATENCY] = "I/O", |
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}; |
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|
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/* |
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* Per-cpu latency histograms: total latency and I/O latency for each scheduling |
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* domain except for KYBER_OTHER. |
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*/ |
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struct kyber_cpu_latency { |
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atomic_t buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS]; |
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}; |
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|
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/* |
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* There is a same mapping between ctx & hctx and kcq & khd, |
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* we use request->mq_ctx->index_hw to index the kcq in khd. |
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*/ |
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struct kyber_ctx_queue { |
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/* |
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* Used to ensure operations on rq_list and kcq_map to be an atmoic one. |
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* Also protect the rqs on rq_list when merge. |
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*/ |
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spinlock_t lock; |
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struct list_head rq_list[KYBER_NUM_DOMAINS]; |
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} ____cacheline_aligned_in_smp; |
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|
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struct kyber_queue_data { |
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struct request_queue *q; |
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|
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/* |
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* Each scheduling domain has a limited number of in-flight requests |
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* device-wide, limited by these tokens. |
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*/ |
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struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS]; |
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|
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/* |
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* Async request percentage, converted to per-word depth for |
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* sbitmap_get_shallow(). |
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*/ |
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unsigned int async_depth; |
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|
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struct kyber_cpu_latency __percpu *cpu_latency; |
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|
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/* Timer for stats aggregation and adjusting domain tokens. */ |
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struct timer_list timer; |
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|
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unsigned int latency_buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS]; |
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|
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unsigned long latency_timeout[KYBER_OTHER]; |
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|
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int domain_p99[KYBER_OTHER]; |
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|
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/* Target latencies in nanoseconds. */ |
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u64 latency_targets[KYBER_OTHER]; |
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}; |
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|
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struct kyber_hctx_data { |
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spinlock_t lock; |
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struct list_head rqs[KYBER_NUM_DOMAINS]; |
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unsigned int cur_domain; |
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unsigned int batching; |
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struct kyber_ctx_queue *kcqs; |
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struct sbitmap kcq_map[KYBER_NUM_DOMAINS]; |
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struct sbq_wait domain_wait[KYBER_NUM_DOMAINS]; |
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struct sbq_wait_state *domain_ws[KYBER_NUM_DOMAINS]; |
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atomic_t wait_index[KYBER_NUM_DOMAINS]; |
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}; |
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|
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static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags, |
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void *key); |
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|
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static unsigned int kyber_sched_domain(unsigned int op) |
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{ |
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switch (op & REQ_OP_MASK) { |
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case REQ_OP_READ: |
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return KYBER_READ; |
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case REQ_OP_WRITE: |
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return KYBER_WRITE; |
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case REQ_OP_DISCARD: |
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return KYBER_DISCARD; |
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default: |
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return KYBER_OTHER; |
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} |
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} |
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|
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static void flush_latency_buckets(struct kyber_queue_data *kqd, |
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struct kyber_cpu_latency *cpu_latency, |
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unsigned int sched_domain, unsigned int type) |
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{ |
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unsigned int *buckets = kqd->latency_buckets[sched_domain][type]; |
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atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type]; |
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unsigned int bucket; |
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|
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for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++) |
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buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0); |
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} |
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|
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/* |
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* Calculate the histogram bucket with the given percentile rank, or -1 if there |
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* aren't enough samples yet. |
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*/ |
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static int calculate_percentile(struct kyber_queue_data *kqd, |
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unsigned int sched_domain, unsigned int type, |
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unsigned int percentile) |
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{ |
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unsigned int *buckets = kqd->latency_buckets[sched_domain][type]; |
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unsigned int bucket, samples = 0, percentile_samples; |
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|
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for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++) |
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samples += buckets[bucket]; |
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|
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if (!samples) |
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return -1; |
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|
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/* |
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* We do the calculation once we have 500 samples or one second passes |
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* since the first sample was recorded, whichever comes first. |
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*/ |
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if (!kqd->latency_timeout[sched_domain]) |
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kqd->latency_timeout[sched_domain] = max(jiffies + HZ, 1UL); |
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if (samples < 500 && |
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time_is_after_jiffies(kqd->latency_timeout[sched_domain])) { |
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return -1; |
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} |
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kqd->latency_timeout[sched_domain] = 0; |
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|
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percentile_samples = DIV_ROUND_UP(samples * percentile, 100); |
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for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS - 1; bucket++) { |
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if (buckets[bucket] >= percentile_samples) |
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break; |
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percentile_samples -= buckets[bucket]; |
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} |
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memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type])); |
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|
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trace_kyber_latency(kqd->q, kyber_domain_names[sched_domain], |
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kyber_latency_type_names[type], percentile, |
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bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples); |
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|
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return bucket; |
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} |
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|
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static void kyber_resize_domain(struct kyber_queue_data *kqd, |
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unsigned int sched_domain, unsigned int depth) |
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{ |
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depth = clamp(depth, 1U, kyber_depth[sched_domain]); |
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if (depth != kqd->domain_tokens[sched_domain].sb.depth) { |
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sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth); |
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trace_kyber_adjust(kqd->q, kyber_domain_names[sched_domain], |
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depth); |
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} |
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} |
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|
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static void kyber_timer_fn(struct timer_list *t) |
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{ |
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struct kyber_queue_data *kqd = from_timer(kqd, t, timer); |
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unsigned int sched_domain; |
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int cpu; |
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bool bad = false; |
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|
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/* Sum all of the per-cpu latency histograms. */ |
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for_each_online_cpu(cpu) { |
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struct kyber_cpu_latency *cpu_latency; |
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|
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cpu_latency = per_cpu_ptr(kqd->cpu_latency, cpu); |
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for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) { |
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flush_latency_buckets(kqd, cpu_latency, sched_domain, |
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KYBER_TOTAL_LATENCY); |
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flush_latency_buckets(kqd, cpu_latency, sched_domain, |
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KYBER_IO_LATENCY); |
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} |
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} |
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|
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/* |
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* Check if any domains have a high I/O latency, which might indicate |
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* congestion in the device. Note that we use the p90; we don't want to |
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* be too sensitive to outliers here. |
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*/ |
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for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) { |
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int p90; |
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|
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p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY, |
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90); |
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if (p90 >= KYBER_GOOD_BUCKETS) |
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bad = true; |
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} |
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|
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/* |
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* Adjust the scheduling domain depths. If we determined that there was |
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* congestion, we throttle all domains with good latencies. Either way, |
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* we ease up on throttling domains with bad latencies. |
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*/ |
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for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) { |
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unsigned int orig_depth, depth; |
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int p99; |
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|
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p99 = calculate_percentile(kqd, sched_domain, |
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KYBER_TOTAL_LATENCY, 99); |
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/* |
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* This is kind of subtle: different domains will not |
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* necessarily have enough samples to calculate the latency |
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* percentiles during the same window, so we have to remember |
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* the p99 for the next time we observe congestion; once we do, |
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* we don't want to throttle again until we get more data, so we |
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* reset it to -1. |
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*/ |
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if (bad) { |
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if (p99 < 0) |
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p99 = kqd->domain_p99[sched_domain]; |
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kqd->domain_p99[sched_domain] = -1; |
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} else if (p99 >= 0) { |
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kqd->domain_p99[sched_domain] = p99; |
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} |
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if (p99 < 0) |
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continue; |
|
|
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/* |
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* If this domain has bad latency, throttle less. Otherwise, |
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* throttle more iff we determined that there is congestion. |
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* |
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* The new depth is scaled linearly with the p99 latency vs the |
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* latency target. E.g., if the p99 is 3/4 of the target, then |
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* we throttle down to 3/4 of the current depth, and if the p99 |
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* is 2x the target, then we double the depth. |
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*/ |
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if (bad || p99 >= KYBER_GOOD_BUCKETS) { |
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orig_depth = kqd->domain_tokens[sched_domain].sb.depth; |
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depth = (orig_depth * (p99 + 1)) >> KYBER_LATENCY_SHIFT; |
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kyber_resize_domain(kqd, sched_domain, depth); |
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} |
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} |
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} |
|
|
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static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q) |
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{ |
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struct kyber_queue_data *kqd; |
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int ret = -ENOMEM; |
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int i; |
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|
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kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node); |
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if (!kqd) |
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goto err; |
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|
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kqd->q = q; |
|
|
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kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency, |
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GFP_KERNEL | __GFP_ZERO); |
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if (!kqd->cpu_latency) |
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goto err_kqd; |
|
|
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timer_setup(&kqd->timer, kyber_timer_fn, 0); |
|
|
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for (i = 0; i < KYBER_NUM_DOMAINS; i++) { |
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WARN_ON(!kyber_depth[i]); |
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WARN_ON(!kyber_batch_size[i]); |
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ret = sbitmap_queue_init_node(&kqd->domain_tokens[i], |
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kyber_depth[i], -1, false, |
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GFP_KERNEL, q->node); |
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if (ret) { |
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while (--i >= 0) |
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sbitmap_queue_free(&kqd->domain_tokens[i]); |
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goto err_buckets; |
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} |
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} |
|
|
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for (i = 0; i < KYBER_OTHER; i++) { |
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kqd->domain_p99[i] = -1; |
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kqd->latency_targets[i] = kyber_latency_targets[i]; |
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} |
|
|
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return kqd; |
|
|
|
err_buckets: |
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free_percpu(kqd->cpu_latency); |
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err_kqd: |
|
kfree(kqd); |
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err: |
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return ERR_PTR(ret); |
|
} |
|
|
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static int kyber_init_sched(struct request_queue *q, struct elevator_type *e) |
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{ |
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struct kyber_queue_data *kqd; |
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struct elevator_queue *eq; |
|
|
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eq = elevator_alloc(q, e); |
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if (!eq) |
|
return -ENOMEM; |
|
|
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kqd = kyber_queue_data_alloc(q); |
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if (IS_ERR(kqd)) { |
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kobject_put(&eq->kobj); |
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return PTR_ERR(kqd); |
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} |
|
|
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blk_stat_enable_accounting(q); |
|
|
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eq->elevator_data = kqd; |
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q->elevator = eq; |
|
|
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return 0; |
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} |
|
|
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static void kyber_exit_sched(struct elevator_queue *e) |
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{ |
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struct kyber_queue_data *kqd = e->elevator_data; |
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int i; |
|
|
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del_timer_sync(&kqd->timer); |
|
|
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for (i = 0; i < KYBER_NUM_DOMAINS; i++) |
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sbitmap_queue_free(&kqd->domain_tokens[i]); |
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free_percpu(kqd->cpu_latency); |
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kfree(kqd); |
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} |
|
|
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static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq) |
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{ |
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unsigned int i; |
|
|
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spin_lock_init(&kcq->lock); |
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for (i = 0; i < KYBER_NUM_DOMAINS; i++) |
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INIT_LIST_HEAD(&kcq->rq_list[i]); |
|
} |
|
|
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static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx) |
|
{ |
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struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data; |
|
struct blk_mq_tags *tags = hctx->sched_tags; |
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unsigned int shift = tags->bitmap_tags->sb.shift; |
|
|
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kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U; |
|
|
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sbitmap_queue_min_shallow_depth(tags->bitmap_tags, kqd->async_depth); |
|
} |
|
|
|
static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx) |
|
{ |
|
struct kyber_hctx_data *khd; |
|
int i; |
|
|
|
khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node); |
|
if (!khd) |
|
return -ENOMEM; |
|
|
|
khd->kcqs = kmalloc_array_node(hctx->nr_ctx, |
|
sizeof(struct kyber_ctx_queue), |
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GFP_KERNEL, hctx->numa_node); |
|
if (!khd->kcqs) |
|
goto err_khd; |
|
|
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for (i = 0; i < hctx->nr_ctx; i++) |
|
kyber_ctx_queue_init(&khd->kcqs[i]); |
|
|
|
for (i = 0; i < KYBER_NUM_DOMAINS; i++) { |
|
if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx, |
|
ilog2(8), GFP_KERNEL, hctx->numa_node, |
|
false, false)) { |
|
while (--i >= 0) |
|
sbitmap_free(&khd->kcq_map[i]); |
|
goto err_kcqs; |
|
} |
|
} |
|
|
|
spin_lock_init(&khd->lock); |
|
|
|
for (i = 0; i < KYBER_NUM_DOMAINS; i++) { |
|
INIT_LIST_HEAD(&khd->rqs[i]); |
|
khd->domain_wait[i].sbq = NULL; |
|
init_waitqueue_func_entry(&khd->domain_wait[i].wait, |
|
kyber_domain_wake); |
|
khd->domain_wait[i].wait.private = hctx; |
|
INIT_LIST_HEAD(&khd->domain_wait[i].wait.entry); |
|
atomic_set(&khd->wait_index[i], 0); |
|
} |
|
|
|
khd->cur_domain = 0; |
|
khd->batching = 0; |
|
|
|
hctx->sched_data = khd; |
|
kyber_depth_updated(hctx); |
|
|
|
return 0; |
|
|
|
err_kcqs: |
|
kfree(khd->kcqs); |
|
err_khd: |
|
kfree(khd); |
|
return -ENOMEM; |
|
} |
|
|
|
static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx) |
|
{ |
|
struct kyber_hctx_data *khd = hctx->sched_data; |
|
int i; |
|
|
|
for (i = 0; i < KYBER_NUM_DOMAINS; i++) |
|
sbitmap_free(&khd->kcq_map[i]); |
|
kfree(khd->kcqs); |
|
kfree(hctx->sched_data); |
|
} |
|
|
|
static int rq_get_domain_token(struct request *rq) |
|
{ |
|
return (long)rq->elv.priv[0]; |
|
} |
|
|
|
static void rq_set_domain_token(struct request *rq, int token) |
|
{ |
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rq->elv.priv[0] = (void *)(long)token; |
|
} |
|
|
|
static void rq_clear_domain_token(struct kyber_queue_data *kqd, |
|
struct request *rq) |
|
{ |
|
unsigned int sched_domain; |
|
int nr; |
|
|
|
nr = rq_get_domain_token(rq); |
|
if (nr != -1) { |
|
sched_domain = kyber_sched_domain(rq->cmd_flags); |
|
sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr, |
|
rq->mq_ctx->cpu); |
|
} |
|
} |
|
|
|
static void kyber_limit_depth(unsigned int op, struct blk_mq_alloc_data *data) |
|
{ |
|
/* |
|
* We use the scheduler tags as per-hardware queue queueing tokens. |
|
* Async requests can be limited at this stage. |
|
*/ |
|
if (!op_is_sync(op)) { |
|
struct kyber_queue_data *kqd = data->q->elevator->elevator_data; |
|
|
|
data->shallow_depth = kqd->async_depth; |
|
} |
|
} |
|
|
|
static bool kyber_bio_merge(struct request_queue *q, struct bio *bio, |
|
unsigned int nr_segs) |
|
{ |
|
struct blk_mq_ctx *ctx = blk_mq_get_ctx(q); |
|
struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, bio->bi_opf, ctx); |
|
struct kyber_hctx_data *khd = hctx->sched_data; |
|
struct kyber_ctx_queue *kcq = &khd->kcqs[ctx->index_hw[hctx->type]]; |
|
unsigned int sched_domain = kyber_sched_domain(bio->bi_opf); |
|
struct list_head *rq_list = &kcq->rq_list[sched_domain]; |
|
bool merged; |
|
|
|
spin_lock(&kcq->lock); |
|
merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs); |
|
spin_unlock(&kcq->lock); |
|
|
|
return merged; |
|
} |
|
|
|
static void kyber_prepare_request(struct request *rq) |
|
{ |
|
rq_set_domain_token(rq, -1); |
|
} |
|
|
|
static void kyber_insert_requests(struct blk_mq_hw_ctx *hctx, |
|
struct list_head *rq_list, bool at_head) |
|
{ |
|
struct kyber_hctx_data *khd = hctx->sched_data; |
|
struct request *rq, *next; |
|
|
|
list_for_each_entry_safe(rq, next, rq_list, queuelist) { |
|
unsigned int sched_domain = kyber_sched_domain(rq->cmd_flags); |
|
struct kyber_ctx_queue *kcq = &khd->kcqs[rq->mq_ctx->index_hw[hctx->type]]; |
|
struct list_head *head = &kcq->rq_list[sched_domain]; |
|
|
|
spin_lock(&kcq->lock); |
|
trace_block_rq_insert(rq); |
|
if (at_head) |
|
list_move(&rq->queuelist, head); |
|
else |
|
list_move_tail(&rq->queuelist, head); |
|
sbitmap_set_bit(&khd->kcq_map[sched_domain], |
|
rq->mq_ctx->index_hw[hctx->type]); |
|
spin_unlock(&kcq->lock); |
|
} |
|
} |
|
|
|
static void kyber_finish_request(struct request *rq) |
|
{ |
|
struct kyber_queue_data *kqd = rq->q->elevator->elevator_data; |
|
|
|
rq_clear_domain_token(kqd, rq); |
|
} |
|
|
|
static void add_latency_sample(struct kyber_cpu_latency *cpu_latency, |
|
unsigned int sched_domain, unsigned int type, |
|
u64 target, u64 latency) |
|
{ |
|
unsigned int bucket; |
|
u64 divisor; |
|
|
|
if (latency > 0) { |
|
divisor = max_t(u64, target >> KYBER_LATENCY_SHIFT, 1); |
|
bucket = min_t(unsigned int, div64_u64(latency - 1, divisor), |
|
KYBER_LATENCY_BUCKETS - 1); |
|
} else { |
|
bucket = 0; |
|
} |
|
|
|
atomic_inc(&cpu_latency->buckets[sched_domain][type][bucket]); |
|
} |
|
|
|
static void kyber_completed_request(struct request *rq, u64 now) |
|
{ |
|
struct kyber_queue_data *kqd = rq->q->elevator->elevator_data; |
|
struct kyber_cpu_latency *cpu_latency; |
|
unsigned int sched_domain; |
|
u64 target; |
|
|
|
sched_domain = kyber_sched_domain(rq->cmd_flags); |
|
if (sched_domain == KYBER_OTHER) |
|
return; |
|
|
|
cpu_latency = get_cpu_ptr(kqd->cpu_latency); |
|
target = kqd->latency_targets[sched_domain]; |
|
add_latency_sample(cpu_latency, sched_domain, KYBER_TOTAL_LATENCY, |
|
target, now - rq->start_time_ns); |
|
add_latency_sample(cpu_latency, sched_domain, KYBER_IO_LATENCY, target, |
|
now - rq->io_start_time_ns); |
|
put_cpu_ptr(kqd->cpu_latency); |
|
|
|
timer_reduce(&kqd->timer, jiffies + HZ / 10); |
|
} |
|
|
|
struct flush_kcq_data { |
|
struct kyber_hctx_data *khd; |
|
unsigned int sched_domain; |
|
struct list_head *list; |
|
}; |
|
|
|
static bool flush_busy_kcq(struct sbitmap *sb, unsigned int bitnr, void *data) |
|
{ |
|
struct flush_kcq_data *flush_data = data; |
|
struct kyber_ctx_queue *kcq = &flush_data->khd->kcqs[bitnr]; |
|
|
|
spin_lock(&kcq->lock); |
|
list_splice_tail_init(&kcq->rq_list[flush_data->sched_domain], |
|
flush_data->list); |
|
sbitmap_clear_bit(sb, bitnr); |
|
spin_unlock(&kcq->lock); |
|
|
|
return true; |
|
} |
|
|
|
static void kyber_flush_busy_kcqs(struct kyber_hctx_data *khd, |
|
unsigned int sched_domain, |
|
struct list_head *list) |
|
{ |
|
struct flush_kcq_data data = { |
|
.khd = khd, |
|
.sched_domain = sched_domain, |
|
.list = list, |
|
}; |
|
|
|
sbitmap_for_each_set(&khd->kcq_map[sched_domain], |
|
flush_busy_kcq, &data); |
|
} |
|
|
|
static int kyber_domain_wake(wait_queue_entry_t *wqe, unsigned mode, int flags, |
|
void *key) |
|
{ |
|
struct blk_mq_hw_ctx *hctx = READ_ONCE(wqe->private); |
|
struct sbq_wait *wait = container_of(wqe, struct sbq_wait, wait); |
|
|
|
sbitmap_del_wait_queue(wait); |
|
blk_mq_run_hw_queue(hctx, true); |
|
return 1; |
|
} |
|
|
|
static int kyber_get_domain_token(struct kyber_queue_data *kqd, |
|
struct kyber_hctx_data *khd, |
|
struct blk_mq_hw_ctx *hctx) |
|
{ |
|
unsigned int sched_domain = khd->cur_domain; |
|
struct sbitmap_queue *domain_tokens = &kqd->domain_tokens[sched_domain]; |
|
struct sbq_wait *wait = &khd->domain_wait[sched_domain]; |
|
struct sbq_wait_state *ws; |
|
int nr; |
|
|
|
nr = __sbitmap_queue_get(domain_tokens); |
|
|
|
/* |
|
* If we failed to get a domain token, make sure the hardware queue is |
|
* run when one becomes available. Note that this is serialized on |
|
* khd->lock, but we still need to be careful about the waker. |
|
*/ |
|
if (nr < 0 && list_empty_careful(&wait->wait.entry)) { |
|
ws = sbq_wait_ptr(domain_tokens, |
|
&khd->wait_index[sched_domain]); |
|
khd->domain_ws[sched_domain] = ws; |
|
sbitmap_add_wait_queue(domain_tokens, ws, wait); |
|
|
|
/* |
|
* Try again in case a token was freed before we got on the wait |
|
* queue. |
|
*/ |
|
nr = __sbitmap_queue_get(domain_tokens); |
|
} |
|
|
|
/* |
|
* If we got a token while we were on the wait queue, remove ourselves |
|
* from the wait queue to ensure that all wake ups make forward |
|
* progress. It's possible that the waker already deleted the entry |
|
* between the !list_empty_careful() check and us grabbing the lock, but |
|
* list_del_init() is okay with that. |
|
*/ |
|
if (nr >= 0 && !list_empty_careful(&wait->wait.entry)) { |
|
ws = khd->domain_ws[sched_domain]; |
|
spin_lock_irq(&ws->wait.lock); |
|
sbitmap_del_wait_queue(wait); |
|
spin_unlock_irq(&ws->wait.lock); |
|
} |
|
|
|
return nr; |
|
} |
|
|
|
static struct request * |
|
kyber_dispatch_cur_domain(struct kyber_queue_data *kqd, |
|
struct kyber_hctx_data *khd, |
|
struct blk_mq_hw_ctx *hctx) |
|
{ |
|
struct list_head *rqs; |
|
struct request *rq; |
|
int nr; |
|
|
|
rqs = &khd->rqs[khd->cur_domain]; |
|
|
|
/* |
|
* If we already have a flushed request, then we just need to get a |
|
* token for it. Otherwise, if there are pending requests in the kcqs, |
|
* flush the kcqs, but only if we can get a token. If not, we should |
|
* leave the requests in the kcqs so that they can be merged. Note that |
|
* khd->lock serializes the flushes, so if we observed any bit set in |
|
* the kcq_map, we will always get a request. |
|
*/ |
|
rq = list_first_entry_or_null(rqs, struct request, queuelist); |
|
if (rq) { |
|
nr = kyber_get_domain_token(kqd, khd, hctx); |
|
if (nr >= 0) { |
|
khd->batching++; |
|
rq_set_domain_token(rq, nr); |
|
list_del_init(&rq->queuelist); |
|
return rq; |
|
} else { |
|
trace_kyber_throttled(kqd->q, |
|
kyber_domain_names[khd->cur_domain]); |
|
} |
|
} else if (sbitmap_any_bit_set(&khd->kcq_map[khd->cur_domain])) { |
|
nr = kyber_get_domain_token(kqd, khd, hctx); |
|
if (nr >= 0) { |
|
kyber_flush_busy_kcqs(khd, khd->cur_domain, rqs); |
|
rq = list_first_entry(rqs, struct request, queuelist); |
|
khd->batching++; |
|
rq_set_domain_token(rq, nr); |
|
list_del_init(&rq->queuelist); |
|
return rq; |
|
} else { |
|
trace_kyber_throttled(kqd->q, |
|
kyber_domain_names[khd->cur_domain]); |
|
} |
|
} |
|
|
|
/* There were either no pending requests or no tokens. */ |
|
return NULL; |
|
} |
|
|
|
static struct request *kyber_dispatch_request(struct blk_mq_hw_ctx *hctx) |
|
{ |
|
struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data; |
|
struct kyber_hctx_data *khd = hctx->sched_data; |
|
struct request *rq; |
|
int i; |
|
|
|
spin_lock(&khd->lock); |
|
|
|
/* |
|
* First, if we are still entitled to batch, try to dispatch a request |
|
* from the batch. |
|
*/ |
|
if (khd->batching < kyber_batch_size[khd->cur_domain]) { |
|
rq = kyber_dispatch_cur_domain(kqd, khd, hctx); |
|
if (rq) |
|
goto out; |
|
} |
|
|
|
/* |
|
* Either, |
|
* 1. We were no longer entitled to a batch. |
|
* 2. The domain we were batching didn't have any requests. |
|
* 3. The domain we were batching was out of tokens. |
|
* |
|
* Start another batch. Note that this wraps back around to the original |
|
* domain if no other domains have requests or tokens. |
|
*/ |
|
khd->batching = 0; |
|
for (i = 0; i < KYBER_NUM_DOMAINS; i++) { |
|
if (khd->cur_domain == KYBER_NUM_DOMAINS - 1) |
|
khd->cur_domain = 0; |
|
else |
|
khd->cur_domain++; |
|
|
|
rq = kyber_dispatch_cur_domain(kqd, khd, hctx); |
|
if (rq) |
|
goto out; |
|
} |
|
|
|
rq = NULL; |
|
out: |
|
spin_unlock(&khd->lock); |
|
return rq; |
|
} |
|
|
|
static bool kyber_has_work(struct blk_mq_hw_ctx *hctx) |
|
{ |
|
struct kyber_hctx_data *khd = hctx->sched_data; |
|
int i; |
|
|
|
for (i = 0; i < KYBER_NUM_DOMAINS; i++) { |
|
if (!list_empty_careful(&khd->rqs[i]) || |
|
sbitmap_any_bit_set(&khd->kcq_map[i])) |
|
return true; |
|
} |
|
|
|
return false; |
|
} |
|
|
|
#define KYBER_LAT_SHOW_STORE(domain, name) \ |
|
static ssize_t kyber_##name##_lat_show(struct elevator_queue *e, \ |
|
char *page) \ |
|
{ \ |
|
struct kyber_queue_data *kqd = e->elevator_data; \ |
|
\ |
|
return sprintf(page, "%llu\n", kqd->latency_targets[domain]); \ |
|
} \ |
|
\ |
|
static ssize_t kyber_##name##_lat_store(struct elevator_queue *e, \ |
|
const char *page, size_t count) \ |
|
{ \ |
|
struct kyber_queue_data *kqd = e->elevator_data; \ |
|
unsigned long long nsec; \ |
|
int ret; \ |
|
\ |
|
ret = kstrtoull(page, 10, &nsec); \ |
|
if (ret) \ |
|
return ret; \ |
|
\ |
|
kqd->latency_targets[domain] = nsec; \ |
|
\ |
|
return count; \ |
|
} |
|
KYBER_LAT_SHOW_STORE(KYBER_READ, read); |
|
KYBER_LAT_SHOW_STORE(KYBER_WRITE, write); |
|
#undef KYBER_LAT_SHOW_STORE |
|
|
|
#define KYBER_LAT_ATTR(op) __ATTR(op##_lat_nsec, 0644, kyber_##op##_lat_show, kyber_##op##_lat_store) |
|
static struct elv_fs_entry kyber_sched_attrs[] = { |
|
KYBER_LAT_ATTR(read), |
|
KYBER_LAT_ATTR(write), |
|
__ATTR_NULL |
|
}; |
|
#undef KYBER_LAT_ATTR |
|
|
|
#ifdef CONFIG_BLK_DEBUG_FS |
|
#define KYBER_DEBUGFS_DOMAIN_ATTRS(domain, name) \ |
|
static int kyber_##name##_tokens_show(void *data, struct seq_file *m) \ |
|
{ \ |
|
struct request_queue *q = data; \ |
|
struct kyber_queue_data *kqd = q->elevator->elevator_data; \ |
|
\ |
|
sbitmap_queue_show(&kqd->domain_tokens[domain], m); \ |
|
return 0; \ |
|
} \ |
|
\ |
|
static void *kyber_##name##_rqs_start(struct seq_file *m, loff_t *pos) \ |
|
__acquires(&khd->lock) \ |
|
{ \ |
|
struct blk_mq_hw_ctx *hctx = m->private; \ |
|
struct kyber_hctx_data *khd = hctx->sched_data; \ |
|
\ |
|
spin_lock(&khd->lock); \ |
|
return seq_list_start(&khd->rqs[domain], *pos); \ |
|
} \ |
|
\ |
|
static void *kyber_##name##_rqs_next(struct seq_file *m, void *v, \ |
|
loff_t *pos) \ |
|
{ \ |
|
struct blk_mq_hw_ctx *hctx = m->private; \ |
|
struct kyber_hctx_data *khd = hctx->sched_data; \ |
|
\ |
|
return seq_list_next(v, &khd->rqs[domain], pos); \ |
|
} \ |
|
\ |
|
static void kyber_##name##_rqs_stop(struct seq_file *m, void *v) \ |
|
__releases(&khd->lock) \ |
|
{ \ |
|
struct blk_mq_hw_ctx *hctx = m->private; \ |
|
struct kyber_hctx_data *khd = hctx->sched_data; \ |
|
\ |
|
spin_unlock(&khd->lock); \ |
|
} \ |
|
\ |
|
static const struct seq_operations kyber_##name##_rqs_seq_ops = { \ |
|
.start = kyber_##name##_rqs_start, \ |
|
.next = kyber_##name##_rqs_next, \ |
|
.stop = kyber_##name##_rqs_stop, \ |
|
.show = blk_mq_debugfs_rq_show, \ |
|
}; \ |
|
\ |
|
static int kyber_##name##_waiting_show(void *data, struct seq_file *m) \ |
|
{ \ |
|
struct blk_mq_hw_ctx *hctx = data; \ |
|
struct kyber_hctx_data *khd = hctx->sched_data; \ |
|
wait_queue_entry_t *wait = &khd->domain_wait[domain].wait; \ |
|
\ |
|
seq_printf(m, "%d\n", !list_empty_careful(&wait->entry)); \ |
|
return 0; \ |
|
} |
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read) |
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_WRITE, write) |
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_DISCARD, discard) |
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_OTHER, other) |
|
#undef KYBER_DEBUGFS_DOMAIN_ATTRS |
|
|
|
static int kyber_async_depth_show(void *data, struct seq_file *m) |
|
{ |
|
struct request_queue *q = data; |
|
struct kyber_queue_data *kqd = q->elevator->elevator_data; |
|
|
|
seq_printf(m, "%u\n", kqd->async_depth); |
|
return 0; |
|
} |
|
|
|
static int kyber_cur_domain_show(void *data, struct seq_file *m) |
|
{ |
|
struct blk_mq_hw_ctx *hctx = data; |
|
struct kyber_hctx_data *khd = hctx->sched_data; |
|
|
|
seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]); |
|
return 0; |
|
} |
|
|
|
static int kyber_batching_show(void *data, struct seq_file *m) |
|
{ |
|
struct blk_mq_hw_ctx *hctx = data; |
|
struct kyber_hctx_data *khd = hctx->sched_data; |
|
|
|
seq_printf(m, "%u\n", khd->batching); |
|
return 0; |
|
} |
|
|
|
#define KYBER_QUEUE_DOMAIN_ATTRS(name) \ |
|
{#name "_tokens", 0400, kyber_##name##_tokens_show} |
|
static const struct blk_mq_debugfs_attr kyber_queue_debugfs_attrs[] = { |
|
KYBER_QUEUE_DOMAIN_ATTRS(read), |
|
KYBER_QUEUE_DOMAIN_ATTRS(write), |
|
KYBER_QUEUE_DOMAIN_ATTRS(discard), |
|
KYBER_QUEUE_DOMAIN_ATTRS(other), |
|
{"async_depth", 0400, kyber_async_depth_show}, |
|
{}, |
|
}; |
|
#undef KYBER_QUEUE_DOMAIN_ATTRS |
|
|
|
#define KYBER_HCTX_DOMAIN_ATTRS(name) \ |
|
{#name "_rqs", 0400, .seq_ops = &kyber_##name##_rqs_seq_ops}, \ |
|
{#name "_waiting", 0400, kyber_##name##_waiting_show} |
|
static const struct blk_mq_debugfs_attr kyber_hctx_debugfs_attrs[] = { |
|
KYBER_HCTX_DOMAIN_ATTRS(read), |
|
KYBER_HCTX_DOMAIN_ATTRS(write), |
|
KYBER_HCTX_DOMAIN_ATTRS(discard), |
|
KYBER_HCTX_DOMAIN_ATTRS(other), |
|
{"cur_domain", 0400, kyber_cur_domain_show}, |
|
{"batching", 0400, kyber_batching_show}, |
|
{}, |
|
}; |
|
#undef KYBER_HCTX_DOMAIN_ATTRS |
|
#endif |
|
|
|
static struct elevator_type kyber_sched = { |
|
.ops = { |
|
.init_sched = kyber_init_sched, |
|
.exit_sched = kyber_exit_sched, |
|
.init_hctx = kyber_init_hctx, |
|
.exit_hctx = kyber_exit_hctx, |
|
.limit_depth = kyber_limit_depth, |
|
.bio_merge = kyber_bio_merge, |
|
.prepare_request = kyber_prepare_request, |
|
.insert_requests = kyber_insert_requests, |
|
.finish_request = kyber_finish_request, |
|
.requeue_request = kyber_finish_request, |
|
.completed_request = kyber_completed_request, |
|
.dispatch_request = kyber_dispatch_request, |
|
.has_work = kyber_has_work, |
|
.depth_updated = kyber_depth_updated, |
|
}, |
|
#ifdef CONFIG_BLK_DEBUG_FS |
|
.queue_debugfs_attrs = kyber_queue_debugfs_attrs, |
|
.hctx_debugfs_attrs = kyber_hctx_debugfs_attrs, |
|
#endif |
|
.elevator_attrs = kyber_sched_attrs, |
|
.elevator_name = "kyber", |
|
.elevator_features = ELEVATOR_F_MQ_AWARE, |
|
.elevator_owner = THIS_MODULE, |
|
}; |
|
|
|
static int __init kyber_init(void) |
|
{ |
|
return elv_register(&kyber_sched); |
|
} |
|
|
|
static void __exit kyber_exit(void) |
|
{ |
|
elv_unregister(&kyber_sched); |
|
} |
|
|
|
module_init(kyber_init); |
|
module_exit(kyber_exit); |
|
|
|
MODULE_AUTHOR("Omar Sandoval"); |
|
MODULE_LICENSE("GPL"); |
|
MODULE_DESCRIPTION("Kyber I/O scheduler");
|
|
|