2017-04-14 08:00:02 +00:00
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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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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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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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#include "blk.h"
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#include "blk-mq.h"
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2017-05-04 07:31:33 +00:00
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#include "blk-mq-debugfs.h"
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2017-04-14 08:00:02 +00:00
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#include "blk-mq-sched.h"
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#include "blk-mq-tag.h"
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#include "blk-stat.h"
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/* Scheduling domains. */
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enum {
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KYBER_READ,
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KYBER_SYNC_WRITE,
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KYBER_OTHER, /* Async writes, discard, etc. */
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KYBER_NUM_DOMAINS,
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};
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enum {
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KYBER_MIN_DEPTH = 256,
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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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* Initial device-wide depths 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
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* the device with only a fraction of the maximum possible queue depth.
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* So, we cap 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_SYNC_WRITE] = 128,
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[KYBER_OTHER] = 64,
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};
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/*
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* Scheduling domain batch sizes. We favor reads.
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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_SYNC_WRITE] = 8,
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[KYBER_OTHER] = 8,
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};
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struct kyber_queue_data {
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struct request_queue *q;
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struct blk_stat_callback *cb;
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/*
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* The device is divided into multiple scheduling domains based on the
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* request type. Each domain has a fixed number of in-flight requests of
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* that type 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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* 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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/* Target latencies in nanoseconds. */
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u64 read_lat_nsec, write_lat_nsec;
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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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2017-06-20 10:06:13 +00:00
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wait_queue_entry_t domain_wait[KYBER_NUM_DOMAINS];
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2017-04-14 08:00:02 +00:00
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atomic_t wait_index[KYBER_NUM_DOMAINS];
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};
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2017-04-20 21:29:16 +00:00
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static int rq_sched_domain(const struct request *rq)
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2017-04-14 08:00:02 +00:00
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{
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unsigned int op = rq->cmd_flags;
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if ((op & REQ_OP_MASK) == REQ_OP_READ)
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return KYBER_READ;
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else if ((op & REQ_OP_MASK) == REQ_OP_WRITE && op_is_sync(op))
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return KYBER_SYNC_WRITE;
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else
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return KYBER_OTHER;
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}
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enum {
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NONE = 0,
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GOOD = 1,
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GREAT = 2,
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BAD = -1,
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AWFUL = -2,
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};
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#define IS_GOOD(status) ((status) > 0)
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#define IS_BAD(status) ((status) < 0)
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static int kyber_lat_status(struct blk_stat_callback *cb,
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unsigned int sched_domain, u64 target)
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{
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u64 latency;
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if (!cb->stat[sched_domain].nr_samples)
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return NONE;
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latency = cb->stat[sched_domain].mean;
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if (latency >= 2 * target)
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return AWFUL;
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else if (latency > target)
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return BAD;
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else if (latency <= target / 2)
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return GREAT;
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else /* (latency <= target) */
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return GOOD;
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}
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/*
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* Adjust the read or synchronous write depth given the status of reads and
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* writes. The goal is that the latencies of the two domains are fair (i.e., if
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* one is good, then the other is good).
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*/
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static void kyber_adjust_rw_depth(struct kyber_queue_data *kqd,
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unsigned int sched_domain, int this_status,
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int other_status)
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{
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unsigned int orig_depth, depth;
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/*
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* If this domain had no samples, or reads and writes are both good or
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* both bad, don't adjust the depth.
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*/
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if (this_status == NONE ||
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(IS_GOOD(this_status) && IS_GOOD(other_status)) ||
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(IS_BAD(this_status) && IS_BAD(other_status)))
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return;
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orig_depth = depth = kqd->domain_tokens[sched_domain].sb.depth;
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if (other_status == NONE) {
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depth++;
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} else {
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switch (this_status) {
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case GOOD:
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if (other_status == AWFUL)
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depth -= max(depth / 4, 1U);
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else
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depth -= max(depth / 8, 1U);
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break;
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case GREAT:
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if (other_status == AWFUL)
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depth /= 2;
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else
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depth -= max(depth / 4, 1U);
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break;
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case BAD:
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depth++;
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break;
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case AWFUL:
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if (other_status == GREAT)
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depth += 2;
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else
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depth++;
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break;
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}
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}
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depth = clamp(depth, 1U, kyber_depth[sched_domain]);
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if (depth != orig_depth)
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sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
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}
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/*
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* Adjust the depth of other requests given the status of reads and synchronous
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* writes. As long as either domain is doing fine, we don't throttle, but if
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* both domains are doing badly, we throttle heavily.
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*/
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static void kyber_adjust_other_depth(struct kyber_queue_data *kqd,
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int read_status, int write_status,
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bool have_samples)
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{
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unsigned int orig_depth, depth;
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int status;
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orig_depth = depth = kqd->domain_tokens[KYBER_OTHER].sb.depth;
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if (read_status == NONE && write_status == NONE) {
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depth += 2;
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} else if (have_samples) {
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if (read_status == NONE)
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status = write_status;
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else if (write_status == NONE)
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status = read_status;
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else
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status = max(read_status, write_status);
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switch (status) {
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case GREAT:
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depth += 2;
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break;
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case GOOD:
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depth++;
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break;
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case BAD:
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depth -= max(depth / 4, 1U);
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break;
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case AWFUL:
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depth /= 2;
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break;
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}
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}
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depth = clamp(depth, 1U, kyber_depth[KYBER_OTHER]);
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if (depth != orig_depth)
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sbitmap_queue_resize(&kqd->domain_tokens[KYBER_OTHER], depth);
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}
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/*
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* Apply heuristics for limiting queue depths based on gathered latency
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* statistics.
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*/
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static void kyber_stat_timer_fn(struct blk_stat_callback *cb)
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{
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struct kyber_queue_data *kqd = cb->data;
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int read_status, write_status;
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read_status = kyber_lat_status(cb, KYBER_READ, kqd->read_lat_nsec);
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write_status = kyber_lat_status(cb, KYBER_SYNC_WRITE, kqd->write_lat_nsec);
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kyber_adjust_rw_depth(kqd, KYBER_READ, read_status, write_status);
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kyber_adjust_rw_depth(kqd, KYBER_SYNC_WRITE, write_status, read_status);
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kyber_adjust_other_depth(kqd, read_status, write_status,
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cb->stat[KYBER_OTHER].nr_samples != 0);
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/*
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* Continue monitoring latencies if we aren't hitting the targets or
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* we're still throttling other requests.
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*/
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if (!blk_stat_is_active(kqd->cb) &&
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((IS_BAD(read_status) || IS_BAD(write_status) ||
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kqd->domain_tokens[KYBER_OTHER].sb.depth < kyber_depth[KYBER_OTHER])))
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blk_stat_activate_msecs(kqd->cb, 100);
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}
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static unsigned int kyber_sched_tags_shift(struct kyber_queue_data *kqd)
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{
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/*
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* All of the hardware queues have the same depth, so we can just grab
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* the shift of the first one.
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*/
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return kqd->q->queue_hw_ctx[0]->sched_tags->bitmap_tags.sb.shift;
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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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unsigned int max_tokens;
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unsigned int shift;
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int ret = -ENOMEM;
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int i;
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kqd = kmalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
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if (!kqd)
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goto err;
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kqd->q = q;
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kqd->cb = blk_stat_alloc_callback(kyber_stat_timer_fn, rq_sched_domain,
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KYBER_NUM_DOMAINS, kqd);
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if (!kqd->cb)
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goto err_kqd;
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/*
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* The maximum number of tokens for any scheduling domain is at least
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* the queue depth of a single hardware queue. If the hardware doesn't
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* have many tags, still provide a reasonable number.
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*/
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max_tokens = max_t(unsigned int, q->tag_set->queue_depth,
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KYBER_MIN_DEPTH);
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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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max_tokens, -1, false, GFP_KERNEL,
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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_cb;
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}
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sbitmap_queue_resize(&kqd->domain_tokens[i], kyber_depth[i]);
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}
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shift = kyber_sched_tags_shift(kqd);
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kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
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kqd->read_lat_nsec = 2000000ULL;
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kqd->write_lat_nsec = 10000000ULL;
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return kqd;
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err_cb:
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blk_stat_free_callback(kqd->cb);
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err_kqd:
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kfree(kqd);
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err:
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return ERR_PTR(ret);
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}
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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)
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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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eq->elevator_data = kqd;
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q->elevator = eq;
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blk_stat_add_callback(q, kqd->cb);
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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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struct request_queue *q = kqd->q;
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int i;
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blk_stat_remove_callback(q, kqd->cb);
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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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blk_stat_free_callback(kqd->cb);
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kfree(kqd);
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}
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static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
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{
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|
|
struct kyber_hctx_data *khd;
|
|
|
|
int i;
|
|
|
|
|
|
|
|
khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node);
|
|
|
|
if (!khd)
|
|
|
|
return -ENOMEM;
|
|
|
|
|
|
|
|
spin_lock_init(&khd->lock);
|
|
|
|
|
|
|
|
for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
|
|
|
|
INIT_LIST_HEAD(&khd->rqs[i]);
|
sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming
So I've noticed a number of instances where it was not obvious from the
code whether ->task_list was for a wait-queue head or a wait-queue entry.
Furthermore, there's a number of wait-queue users where the lists are
not for 'tasks' but other entities (poll tables, etc.), in which case
the 'task_list' name is actively confusing.
To clear this all up, name the wait-queue head and entry list structure
fields unambiguously:
struct wait_queue_head::task_list => ::head
struct wait_queue_entry::task_list => ::entry
For example, this code:
rqw->wait.task_list.next != &wait->task_list
... is was pretty unclear (to me) what it's doing, while now it's written this way:
rqw->wait.head.next != &wait->entry
... which makes it pretty clear that we are iterating a list until we see the head.
Other examples are:
list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
list_for_each_entry(wq, &fence->wait.task_list, task_list) {
... where it's unclear (to me) what we are iterating, and during review it's
hard to tell whether it's trying to walk a wait-queue entry (which would be
a bug), while now it's written as:
list_for_each_entry_safe(pos, next, &x->head, entry) {
list_for_each_entry(wq, &fence->wait.head, entry) {
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-20 10:06:46 +00:00
|
|
|
INIT_LIST_HEAD(&khd->domain_wait[i].entry);
|
2017-04-14 08:00:02 +00:00
|
|
|
atomic_set(&khd->wait_index[i], 0);
|
|
|
|
}
|
|
|
|
|
|
|
|
khd->cur_domain = 0;
|
|
|
|
khd->batching = 0;
|
|
|
|
|
|
|
|
hctx->sched_data = khd;
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
|
|
|
|
{
|
|
|
|
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)
|
|
|
|
{
|
|
|
|
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 = rq_sched_domain(rq);
|
|
|
|
sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr,
|
|
|
|
rq->mq_ctx->cpu);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
static struct request *kyber_get_request(struct request_queue *q,
|
|
|
|
unsigned int op,
|
|
|
|
struct blk_mq_alloc_data *data)
|
|
|
|
{
|
|
|
|
struct kyber_queue_data *kqd = q->elevator->elevator_data;
|
|
|
|
struct request *rq;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* We use the scheduler tags as per-hardware queue queueing tokens.
|
|
|
|
* Async requests can be limited at this stage.
|
|
|
|
*/
|
|
|
|
if (!op_is_sync(op))
|
|
|
|
data->shallow_depth = kqd->async_depth;
|
|
|
|
|
|
|
|
rq = __blk_mq_alloc_request(data, op);
|
|
|
|
if (rq)
|
|
|
|
rq_set_domain_token(rq, -1);
|
|
|
|
return rq;
|
|
|
|
}
|
|
|
|
|
|
|
|
static void kyber_put_request(struct request *rq)
|
|
|
|
{
|
|
|
|
struct request_queue *q = rq->q;
|
|
|
|
struct kyber_queue_data *kqd = q->elevator->elevator_data;
|
|
|
|
|
|
|
|
rq_clear_domain_token(kqd, rq);
|
|
|
|
blk_mq_finish_request(rq);
|
|
|
|
}
|
|
|
|
|
|
|
|
static void kyber_completed_request(struct request *rq)
|
|
|
|
{
|
|
|
|
struct request_queue *q = rq->q;
|
|
|
|
struct kyber_queue_data *kqd = q->elevator->elevator_data;
|
|
|
|
unsigned int sched_domain;
|
|
|
|
u64 now, latency, target;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Check if this request met our latency goal. If not, quickly gather
|
|
|
|
* some statistics and start throttling.
|
|
|
|
*/
|
|
|
|
sched_domain = rq_sched_domain(rq);
|
|
|
|
switch (sched_domain) {
|
|
|
|
case KYBER_READ:
|
|
|
|
target = kqd->read_lat_nsec;
|
|
|
|
break;
|
|
|
|
case KYBER_SYNC_WRITE:
|
|
|
|
target = kqd->write_lat_nsec;
|
|
|
|
break;
|
|
|
|
default:
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* If we are already monitoring latencies, don't check again. */
|
|
|
|
if (blk_stat_is_active(kqd->cb))
|
|
|
|
return;
|
|
|
|
|
|
|
|
now = __blk_stat_time(ktime_to_ns(ktime_get()));
|
|
|
|
if (now < blk_stat_time(&rq->issue_stat))
|
|
|
|
return;
|
|
|
|
|
|
|
|
latency = now - blk_stat_time(&rq->issue_stat);
|
|
|
|
|
|
|
|
if (latency > target)
|
|
|
|
blk_stat_activate_msecs(kqd->cb, 10);
|
|
|
|
}
|
|
|
|
|
|
|
|
static void kyber_flush_busy_ctxs(struct kyber_hctx_data *khd,
|
|
|
|
struct blk_mq_hw_ctx *hctx)
|
|
|
|
{
|
|
|
|
LIST_HEAD(rq_list);
|
|
|
|
struct request *rq, *next;
|
|
|
|
|
|
|
|
blk_mq_flush_busy_ctxs(hctx, &rq_list);
|
|
|
|
list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
|
|
|
|
unsigned int sched_domain;
|
|
|
|
|
|
|
|
sched_domain = rq_sched_domain(rq);
|
|
|
|
list_move_tail(&rq->queuelist, &khd->rqs[sched_domain]);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2017-06-20 10:06:13 +00:00
|
|
|
static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
|
2017-04-14 08:00:02 +00:00
|
|
|
void *key)
|
|
|
|
{
|
|
|
|
struct blk_mq_hw_ctx *hctx = READ_ONCE(wait->private);
|
|
|
|
|
sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming
So I've noticed a number of instances where it was not obvious from the
code whether ->task_list was for a wait-queue head or a wait-queue entry.
Furthermore, there's a number of wait-queue users where the lists are
not for 'tasks' but other entities (poll tables, etc.), in which case
the 'task_list' name is actively confusing.
To clear this all up, name the wait-queue head and entry list structure
fields unambiguously:
struct wait_queue_head::task_list => ::head
struct wait_queue_entry::task_list => ::entry
For example, this code:
rqw->wait.task_list.next != &wait->task_list
... is was pretty unclear (to me) what it's doing, while now it's written this way:
rqw->wait.head.next != &wait->entry
... which makes it pretty clear that we are iterating a list until we see the head.
Other examples are:
list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
list_for_each_entry(wq, &fence->wait.task_list, task_list) {
... where it's unclear (to me) what we are iterating, and during review it's
hard to tell whether it's trying to walk a wait-queue entry (which would be
a bug), while now it's written as:
list_for_each_entry_safe(pos, next, &x->head, entry) {
list_for_each_entry(wq, &fence->wait.head, entry) {
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-20 10:06:46 +00:00
|
|
|
list_del_init(&wait->entry);
|
2017-04-14 08:00:02 +00:00
|
|
|
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];
|
2017-06-20 10:06:13 +00:00
|
|
|
wait_queue_entry_t *wait = &khd->domain_wait[sched_domain];
|
2017-04-14 08:00:02 +00:00
|
|
|
struct sbq_wait_state *ws;
|
|
|
|
int nr;
|
|
|
|
|
|
|
|
nr = __sbitmap_queue_get(domain_tokens);
|
|
|
|
if (nr >= 0)
|
|
|
|
return nr;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* 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.
|
|
|
|
*/
|
sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming
So I've noticed a number of instances where it was not obvious from the
code whether ->task_list was for a wait-queue head or a wait-queue entry.
Furthermore, there's a number of wait-queue users where the lists are
not for 'tasks' but other entities (poll tables, etc.), in which case
the 'task_list' name is actively confusing.
To clear this all up, name the wait-queue head and entry list structure
fields unambiguously:
struct wait_queue_head::task_list => ::head
struct wait_queue_entry::task_list => ::entry
For example, this code:
rqw->wait.task_list.next != &wait->task_list
... is was pretty unclear (to me) what it's doing, while now it's written this way:
rqw->wait.head.next != &wait->entry
... which makes it pretty clear that we are iterating a list until we see the head.
Other examples are:
list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
list_for_each_entry(wq, &fence->wait.task_list, task_list) {
... where it's unclear (to me) what we are iterating, and during review it's
hard to tell whether it's trying to walk a wait-queue entry (which would be
a bug), while now it's written as:
list_for_each_entry_safe(pos, next, &x->head, entry) {
list_for_each_entry(wq, &fence->wait.head, entry) {
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-20 10:06:46 +00:00
|
|
|
if (list_empty_careful(&wait->entry)) {
|
2017-04-14 08:00:02 +00:00
|
|
|
init_waitqueue_func_entry(wait, kyber_domain_wake);
|
|
|
|
wait->private = hctx;
|
|
|
|
ws = sbq_wait_ptr(domain_tokens,
|
|
|
|
&khd->wait_index[sched_domain]);
|
|
|
|
add_wait_queue(&ws->wait, wait);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Try again in case a token was freed before we got on the wait
|
|
|
|
* queue.
|
|
|
|
*/
|
|
|
|
nr = __sbitmap_queue_get(domain_tokens);
|
|
|
|
}
|
|
|
|
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,
|
|
|
|
bool *flushed)
|
|
|
|
{
|
|
|
|
struct list_head *rqs;
|
|
|
|
struct request *rq;
|
|
|
|
int nr;
|
|
|
|
|
|
|
|
rqs = &khd->rqs[khd->cur_domain];
|
|
|
|
rq = list_first_entry_or_null(rqs, struct request, queuelist);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* If there wasn't already a pending request and we haven't flushed the
|
|
|
|
* software queues yet, flush the software queues and check again.
|
|
|
|
*/
|
|
|
|
if (!rq && !*flushed) {
|
|
|
|
kyber_flush_busy_ctxs(khd, hctx);
|
|
|
|
*flushed = true;
|
|
|
|
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;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/* 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;
|
|
|
|
bool flushed = false;
|
|
|
|
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, &flushed);
|
|
|
|
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, &flushed);
|
|
|
|
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]))
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
|
|
|
#define KYBER_LAT_SHOW_STORE(op) \
|
|
|
|
static ssize_t kyber_##op##_lat_show(struct elevator_queue *e, \
|
|
|
|
char *page) \
|
|
|
|
{ \
|
|
|
|
struct kyber_queue_data *kqd = e->elevator_data; \
|
|
|
|
\
|
|
|
|
return sprintf(page, "%llu\n", kqd->op##_lat_nsec); \
|
|
|
|
} \
|
|
|
|
\
|
|
|
|
static ssize_t kyber_##op##_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->op##_lat_nsec = nsec; \
|
|
|
|
\
|
|
|
|
return count; \
|
|
|
|
}
|
|
|
|
KYBER_LAT_SHOW_STORE(read);
|
|
|
|
KYBER_LAT_SHOW_STORE(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
|
|
|
|
|
2017-05-04 07:31:33 +00:00
|
|
|
#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; \
|
2017-06-20 10:06:13 +00:00
|
|
|
wait_queue_entry_t *wait = &khd->domain_wait[domain]; \
|
2017-05-04 07:31:33 +00:00
|
|
|
\
|
sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming
So I've noticed a number of instances where it was not obvious from the
code whether ->task_list was for a wait-queue head or a wait-queue entry.
Furthermore, there's a number of wait-queue users where the lists are
not for 'tasks' but other entities (poll tables, etc.), in which case
the 'task_list' name is actively confusing.
To clear this all up, name the wait-queue head and entry list structure
fields unambiguously:
struct wait_queue_head::task_list => ::head
struct wait_queue_entry::task_list => ::entry
For example, this code:
rqw->wait.task_list.next != &wait->task_list
... is was pretty unclear (to me) what it's doing, while now it's written this way:
rqw->wait.head.next != &wait->entry
... which makes it pretty clear that we are iterating a list until we see the head.
Other examples are:
list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
list_for_each_entry(wq, &fence->wait.task_list, task_list) {
... where it's unclear (to me) what we are iterating, and during review it's
hard to tell whether it's trying to walk a wait-queue entry (which would be
a bug), while now it's written as:
list_for_each_entry_safe(pos, next, &x->head, entry) {
list_for_each_entry(wq, &fence->wait.head, entry) {
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-20 10:06:46 +00:00
|
|
|
seq_printf(m, "%d\n", !list_empty_careful(&wait->entry)); \
|
2017-05-04 07:31:33 +00:00
|
|
|
return 0; \
|
|
|
|
}
|
|
|
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)
|
|
|
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_SYNC_WRITE, sync_write)
|
|
|
|
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;
|
|
|
|
|
|
|
|
switch (khd->cur_domain) {
|
|
|
|
case KYBER_READ:
|
|
|
|
seq_puts(m, "READ\n");
|
|
|
|
break;
|
|
|
|
case KYBER_SYNC_WRITE:
|
|
|
|
seq_puts(m, "SYNC_WRITE\n");
|
|
|
|
break;
|
|
|
|
case KYBER_OTHER:
|
|
|
|
seq_puts(m, "OTHER\n");
|
|
|
|
break;
|
|
|
|
default:
|
|
|
|
seq_printf(m, "%u\n", khd->cur_domain);
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
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(sync_write),
|
|
|
|
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(sync_write),
|
|
|
|
KYBER_HCTX_DOMAIN_ATTRS(other),
|
|
|
|
{"cur_domain", 0400, kyber_cur_domain_show},
|
|
|
|
{"batching", 0400, kyber_batching_show},
|
|
|
|
{},
|
|
|
|
};
|
|
|
|
#undef KYBER_HCTX_DOMAIN_ATTRS
|
|
|
|
#endif
|
|
|
|
|
2017-04-14 08:00:02 +00:00
|
|
|
static struct elevator_type kyber_sched = {
|
|
|
|
.ops.mq = {
|
|
|
|
.init_sched = kyber_init_sched,
|
|
|
|
.exit_sched = kyber_exit_sched,
|
|
|
|
.init_hctx = kyber_init_hctx,
|
|
|
|
.exit_hctx = kyber_exit_hctx,
|
|
|
|
.get_request = kyber_get_request,
|
|
|
|
.put_request = kyber_put_request,
|
|
|
|
.completed_request = kyber_completed_request,
|
|
|
|
.dispatch_request = kyber_dispatch_request,
|
|
|
|
.has_work = kyber_has_work,
|
|
|
|
},
|
|
|
|
.uses_mq = true,
|
2017-05-04 07:31:33 +00:00
|
|
|
#ifdef CONFIG_BLK_DEBUG_FS
|
|
|
|
.queue_debugfs_attrs = kyber_queue_debugfs_attrs,
|
|
|
|
.hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,
|
|
|
|
#endif
|
2017-04-14 08:00:02 +00:00
|
|
|
.elevator_attrs = kyber_sched_attrs,
|
|
|
|
.elevator_name = "kyber",
|
|
|
|
.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");
|