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1057 lines
28 KiB
1057 lines
28 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Block rq-qos base io controller |
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* |
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* This works similar to wbt with a few exceptions |
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* |
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* - It's bio based, so the latency covers the whole block layer in addition to |
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* the actual io. |
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* - We will throttle all IO that comes in here if we need to. |
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* - We use the mean latency over the 100ms window. This is because writes can |
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* be particularly fast, which could give us a false sense of the impact of |
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* other workloads on our protected workload. |
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* - By default there's no throttling, we set the queue_depth to UINT_MAX so |
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* that we can have as many outstanding bio's as we're allowed to. Only at |
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* throttle time do we pay attention to the actual queue depth. |
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* |
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* The hierarchy works like the cpu controller does, we track the latency at |
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* every configured node, and each configured node has it's own independent |
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* queue depth. This means that we only care about our latency targets at the |
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* peer level. Some group at the bottom of the hierarchy isn't going to affect |
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* a group at the end of some other path if we're only configred at leaf level. |
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* |
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* Consider the following |
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* |
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* root blkg |
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* / \ |
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* fast (target=5ms) slow (target=10ms) |
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* / \ / \ |
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* a b normal(15ms) unloved |
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* |
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* "a" and "b" have no target, but their combined io under "fast" cannot exceed |
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* an average latency of 5ms. If it does then we will throttle the "slow" |
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* group. In the case of "normal", if it exceeds its 15ms target, we will |
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* throttle "unloved", but nobody else. |
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* |
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* In this example "fast", "slow", and "normal" will be the only groups actually |
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* accounting their io latencies. We have to walk up the heirarchy to the root |
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* on every submit and complete so we can do the appropriate stat recording and |
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* adjust the queue depth of ourselves if needed. |
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* |
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* There are 2 ways we throttle IO. |
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* |
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* 1) Queue depth throttling. As we throttle down we will adjust the maximum |
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* number of IO's we're allowed to have in flight. This starts at (u64)-1 down |
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* to 1. If the group is only ever submitting IO for itself then this is the |
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* only way we throttle. |
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* |
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* 2) Induced delay throttling. This is for the case that a group is generating |
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* IO that has to be issued by the root cg to avoid priority inversion. So think |
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* REQ_META or REQ_SWAP. If we are already at qd == 1 and we're getting a lot |
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* of work done for us on behalf of the root cg and are being asked to scale |
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* down more then we induce a latency at userspace return. We accumulate the |
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* total amount of time we need to be punished by doing |
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* |
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* total_time += min_lat_nsec - actual_io_completion |
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* |
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* and then at throttle time will do |
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* |
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* throttle_time = min(total_time, NSEC_PER_SEC) |
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* |
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* This induced delay will throttle back the activity that is generating the |
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* root cg issued io's, wethere that's some metadata intensive operation or the |
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* group is using so much memory that it is pushing us into swap. |
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* |
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* Copyright (C) 2018 Josef Bacik |
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*/ |
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#include <linux/kernel.h> |
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#include <linux/blk_types.h> |
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#include <linux/backing-dev.h> |
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#include <linux/module.h> |
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#include <linux/timer.h> |
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#include <linux/memcontrol.h> |
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#include <linux/sched/loadavg.h> |
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#include <linux/sched/signal.h> |
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#include <trace/events/block.h> |
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#include <linux/blk-mq.h> |
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#include "blk-rq-qos.h" |
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#include "blk-stat.h" |
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#include "blk.h" |
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|
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#define DEFAULT_SCALE_COOKIE 1000000U |
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|
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static struct blkcg_policy blkcg_policy_iolatency; |
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struct iolatency_grp; |
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|
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struct blk_iolatency { |
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struct rq_qos rqos; |
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struct timer_list timer; |
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atomic_t enabled; |
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}; |
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|
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static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos) |
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{ |
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return container_of(rqos, struct blk_iolatency, rqos); |
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} |
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|
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static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat) |
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{ |
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return atomic_read(&blkiolat->enabled) > 0; |
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} |
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|
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struct child_latency_info { |
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spinlock_t lock; |
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|
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/* Last time we adjusted the scale of everybody. */ |
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u64 last_scale_event; |
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|
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/* The latency that we missed. */ |
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u64 scale_lat; |
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|
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/* Total io's from all of our children for the last summation. */ |
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u64 nr_samples; |
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|
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/* The guy who actually changed the latency numbers. */ |
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struct iolatency_grp *scale_grp; |
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|
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/* Cookie to tell if we need to scale up or down. */ |
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atomic_t scale_cookie; |
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}; |
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|
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struct percentile_stats { |
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u64 total; |
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u64 missed; |
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}; |
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|
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struct latency_stat { |
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union { |
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struct percentile_stats ps; |
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struct blk_rq_stat rqs; |
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}; |
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}; |
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|
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struct iolatency_grp { |
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struct blkg_policy_data pd; |
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struct latency_stat __percpu *stats; |
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struct latency_stat cur_stat; |
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struct blk_iolatency *blkiolat; |
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struct rq_depth rq_depth; |
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struct rq_wait rq_wait; |
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atomic64_t window_start; |
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atomic_t scale_cookie; |
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u64 min_lat_nsec; |
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u64 cur_win_nsec; |
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|
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/* total running average of our io latency. */ |
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u64 lat_avg; |
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|
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/* Our current number of IO's for the last summation. */ |
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u64 nr_samples; |
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|
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bool ssd; |
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struct child_latency_info child_lat; |
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}; |
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|
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#define BLKIOLATENCY_MIN_WIN_SIZE (100 * NSEC_PER_MSEC) |
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#define BLKIOLATENCY_MAX_WIN_SIZE NSEC_PER_SEC |
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/* |
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* These are the constants used to fake the fixed-point moving average |
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* calculation just like load average. The call to calc_load() folds |
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* (FIXED_1 (2048) - exp_factor) * new_sample into lat_avg. The sampling |
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* window size is bucketed to try to approximately calculate average |
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* latency such that 1/exp (decay rate) is [1 min, 2.5 min) when windows |
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* elapse immediately. Note, windows only elapse with IO activity. Idle |
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* periods extend the most recent window. |
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*/ |
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#define BLKIOLATENCY_NR_EXP_FACTORS 5 |
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#define BLKIOLATENCY_EXP_BUCKET_SIZE (BLKIOLATENCY_MAX_WIN_SIZE / \ |
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(BLKIOLATENCY_NR_EXP_FACTORS - 1)) |
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static const u64 iolatency_exp_factors[BLKIOLATENCY_NR_EXP_FACTORS] = { |
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2045, // exp(1/600) - 600 samples |
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2039, // exp(1/240) - 240 samples |
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2031, // exp(1/120) - 120 samples |
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2023, // exp(1/80) - 80 samples |
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2014, // exp(1/60) - 60 samples |
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}; |
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|
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static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd) |
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{ |
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return pd ? container_of(pd, struct iolatency_grp, pd) : NULL; |
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} |
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static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg) |
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{ |
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return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency)); |
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} |
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|
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static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat) |
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{ |
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return pd_to_blkg(&iolat->pd); |
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} |
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|
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static inline void latency_stat_init(struct iolatency_grp *iolat, |
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struct latency_stat *stat) |
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{ |
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if (iolat->ssd) { |
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stat->ps.total = 0; |
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stat->ps.missed = 0; |
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} else |
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blk_rq_stat_init(&stat->rqs); |
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} |
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|
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static inline void latency_stat_sum(struct iolatency_grp *iolat, |
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struct latency_stat *sum, |
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struct latency_stat *stat) |
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{ |
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if (iolat->ssd) { |
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sum->ps.total += stat->ps.total; |
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sum->ps.missed += stat->ps.missed; |
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} else |
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blk_rq_stat_sum(&sum->rqs, &stat->rqs); |
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} |
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|
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static inline void latency_stat_record_time(struct iolatency_grp *iolat, |
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u64 req_time) |
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{ |
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struct latency_stat *stat = get_cpu_ptr(iolat->stats); |
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if (iolat->ssd) { |
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if (req_time >= iolat->min_lat_nsec) |
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stat->ps.missed++; |
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stat->ps.total++; |
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} else |
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blk_rq_stat_add(&stat->rqs, req_time); |
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put_cpu_ptr(stat); |
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} |
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|
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static inline bool latency_sum_ok(struct iolatency_grp *iolat, |
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struct latency_stat *stat) |
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{ |
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if (iolat->ssd) { |
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u64 thresh = div64_u64(stat->ps.total, 10); |
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thresh = max(thresh, 1ULL); |
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return stat->ps.missed < thresh; |
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} |
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return stat->rqs.mean <= iolat->min_lat_nsec; |
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} |
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|
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static inline u64 latency_stat_samples(struct iolatency_grp *iolat, |
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struct latency_stat *stat) |
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{ |
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if (iolat->ssd) |
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return stat->ps.total; |
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return stat->rqs.nr_samples; |
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} |
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|
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static inline void iolat_update_total_lat_avg(struct iolatency_grp *iolat, |
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struct latency_stat *stat) |
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{ |
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int exp_idx; |
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|
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if (iolat->ssd) |
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return; |
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|
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/* |
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* calc_load() takes in a number stored in fixed point representation. |
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* Because we are using this for IO time in ns, the values stored |
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* are significantly larger than the FIXED_1 denominator (2048). |
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* Therefore, rounding errors in the calculation are negligible and |
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* can be ignored. |
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*/ |
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exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1, |
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div64_u64(iolat->cur_win_nsec, |
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BLKIOLATENCY_EXP_BUCKET_SIZE)); |
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iolat->lat_avg = calc_load(iolat->lat_avg, |
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iolatency_exp_factors[exp_idx], |
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stat->rqs.mean); |
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} |
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static void iolat_cleanup_cb(struct rq_wait *rqw, void *private_data) |
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{ |
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atomic_dec(&rqw->inflight); |
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wake_up(&rqw->wait); |
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} |
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static bool iolat_acquire_inflight(struct rq_wait *rqw, void *private_data) |
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{ |
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struct iolatency_grp *iolat = private_data; |
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return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth); |
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} |
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static void __blkcg_iolatency_throttle(struct rq_qos *rqos, |
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struct iolatency_grp *iolat, |
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bool issue_as_root, |
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bool use_memdelay) |
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{ |
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struct rq_wait *rqw = &iolat->rq_wait; |
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unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay); |
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if (use_delay) |
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blkcg_schedule_throttle(rqos->q, use_memdelay); |
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/* |
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* To avoid priority inversions we want to just take a slot if we are |
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* issuing as root. If we're being killed off there's no point in |
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* delaying things, we may have been killed by OOM so throttling may |
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* make recovery take even longer, so just let the IO's through so the |
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* task can go away. |
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*/ |
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if (issue_as_root || fatal_signal_pending(current)) { |
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atomic_inc(&rqw->inflight); |
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return; |
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} |
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rq_qos_wait(rqw, iolat, iolat_acquire_inflight, iolat_cleanup_cb); |
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} |
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#define SCALE_DOWN_FACTOR 2 |
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#define SCALE_UP_FACTOR 4 |
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static inline unsigned long scale_amount(unsigned long qd, bool up) |
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{ |
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return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL); |
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} |
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|
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/* |
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* We scale the qd down faster than we scale up, so we need to use this helper |
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* to adjust the scale_cookie accordingly so we don't prematurely get |
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* scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much. |
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* |
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* Each group has their own local copy of the last scale cookie they saw, so if |
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* the global scale cookie goes up or down they know which way they need to go |
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* based on their last knowledge of it. |
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*/ |
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static void scale_cookie_change(struct blk_iolatency *blkiolat, |
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struct child_latency_info *lat_info, |
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bool up) |
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{ |
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unsigned long qd = blkiolat->rqos.q->nr_requests; |
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unsigned long scale = scale_amount(qd, up); |
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unsigned long old = atomic_read(&lat_info->scale_cookie); |
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unsigned long max_scale = qd << 1; |
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unsigned long diff = 0; |
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|
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if (old < DEFAULT_SCALE_COOKIE) |
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diff = DEFAULT_SCALE_COOKIE - old; |
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if (up) { |
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if (scale + old > DEFAULT_SCALE_COOKIE) |
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atomic_set(&lat_info->scale_cookie, |
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DEFAULT_SCALE_COOKIE); |
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else if (diff > qd) |
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atomic_inc(&lat_info->scale_cookie); |
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else |
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atomic_add(scale, &lat_info->scale_cookie); |
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} else { |
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/* |
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* We don't want to dig a hole so deep that it takes us hours to |
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* dig out of it. Just enough that we don't throttle/unthrottle |
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* with jagged workloads but can still unthrottle once pressure |
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* has sufficiently dissipated. |
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*/ |
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if (diff > qd) { |
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if (diff < max_scale) |
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atomic_dec(&lat_info->scale_cookie); |
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} else { |
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atomic_sub(scale, &lat_info->scale_cookie); |
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} |
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} |
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} |
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|
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/* |
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* Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the |
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* queue depth at a time so we don't get wild swings and hopefully dial in to |
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* fairer distribution of the overall queue depth. |
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*/ |
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static void scale_change(struct iolatency_grp *iolat, bool up) |
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{ |
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unsigned long qd = iolat->blkiolat->rqos.q->nr_requests; |
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unsigned long scale = scale_amount(qd, up); |
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unsigned long old = iolat->rq_depth.max_depth; |
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if (old > qd) |
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old = qd; |
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if (up) { |
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if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat))) |
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return; |
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|
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if (old < qd) { |
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old += scale; |
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old = min(old, qd); |
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iolat->rq_depth.max_depth = old; |
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wake_up_all(&iolat->rq_wait.wait); |
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} |
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} else { |
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old >>= 1; |
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iolat->rq_depth.max_depth = max(old, 1UL); |
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} |
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} |
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|
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/* Check our parent and see if the scale cookie has changed. */ |
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static void check_scale_change(struct iolatency_grp *iolat) |
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{ |
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struct iolatency_grp *parent; |
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struct child_latency_info *lat_info; |
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unsigned int cur_cookie; |
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unsigned int our_cookie = atomic_read(&iolat->scale_cookie); |
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u64 scale_lat; |
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unsigned int old; |
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int direction = 0; |
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|
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if (lat_to_blkg(iolat)->parent == NULL) |
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return; |
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|
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parent = blkg_to_lat(lat_to_blkg(iolat)->parent); |
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if (!parent) |
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return; |
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|
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lat_info = &parent->child_lat; |
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cur_cookie = atomic_read(&lat_info->scale_cookie); |
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scale_lat = READ_ONCE(lat_info->scale_lat); |
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|
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if (cur_cookie < our_cookie) |
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direction = -1; |
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else if (cur_cookie > our_cookie) |
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direction = 1; |
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else |
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return; |
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|
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old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie); |
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|
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/* Somebody beat us to the punch, just bail. */ |
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if (old != our_cookie) |
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return; |
|
|
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if (direction < 0 && iolat->min_lat_nsec) { |
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u64 samples_thresh; |
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|
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if (!scale_lat || iolat->min_lat_nsec <= scale_lat) |
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return; |
|
|
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/* |
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* Sometimes high priority groups are their own worst enemy, so |
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* instead of taking it out on some poor other group that did 5% |
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* or less of the IO's for the last summation just skip this |
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* scale down event. |
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*/ |
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samples_thresh = lat_info->nr_samples * 5; |
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samples_thresh = max(1ULL, div64_u64(samples_thresh, 100)); |
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if (iolat->nr_samples <= samples_thresh) |
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return; |
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} |
|
|
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/* We're as low as we can go. */ |
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if (iolat->rq_depth.max_depth == 1 && direction < 0) { |
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blkcg_use_delay(lat_to_blkg(iolat)); |
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return; |
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} |
|
|
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/* We're back to the default cookie, unthrottle all the things. */ |
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if (cur_cookie == DEFAULT_SCALE_COOKIE) { |
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blkcg_clear_delay(lat_to_blkg(iolat)); |
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iolat->rq_depth.max_depth = UINT_MAX; |
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wake_up_all(&iolat->rq_wait.wait); |
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return; |
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} |
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|
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scale_change(iolat, direction > 0); |
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} |
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|
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static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio) |
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{ |
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struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); |
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struct blkcg_gq *blkg = bio->bi_blkg; |
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bool issue_as_root = bio_issue_as_root_blkg(bio); |
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|
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if (!blk_iolatency_enabled(blkiolat)) |
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return; |
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|
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while (blkg && blkg->parent) { |
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struct iolatency_grp *iolat = blkg_to_lat(blkg); |
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if (!iolat) { |
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blkg = blkg->parent; |
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continue; |
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} |
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|
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check_scale_change(iolat); |
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__blkcg_iolatency_throttle(rqos, iolat, issue_as_root, |
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(bio->bi_opf & REQ_SWAP) == REQ_SWAP); |
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blkg = blkg->parent; |
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} |
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if (!timer_pending(&blkiolat->timer)) |
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mod_timer(&blkiolat->timer, jiffies + HZ); |
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} |
|
|
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static void iolatency_record_time(struct iolatency_grp *iolat, |
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struct bio_issue *issue, u64 now, |
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bool issue_as_root) |
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{ |
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u64 start = bio_issue_time(issue); |
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u64 req_time; |
|
|
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/* |
|
* Have to do this so we are truncated to the correct time that our |
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* issue is truncated to. |
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*/ |
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now = __bio_issue_time(now); |
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|
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if (now <= start) |
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return; |
|
|
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req_time = now - start; |
|
|
|
/* |
|
* We don't want to count issue_as_root bio's in the cgroups latency |
|
* statistics as it could skew the numbers downwards. |
|
*/ |
|
if (unlikely(issue_as_root && iolat->rq_depth.max_depth != UINT_MAX)) { |
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u64 sub = iolat->min_lat_nsec; |
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if (req_time < sub) |
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blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time); |
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return; |
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} |
|
|
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latency_stat_record_time(iolat, req_time); |
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} |
|
|
|
#define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC) |
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#define BLKIOLATENCY_MIN_GOOD_SAMPLES 5 |
|
|
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static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now) |
|
{ |
|
struct blkcg_gq *blkg = lat_to_blkg(iolat); |
|
struct iolatency_grp *parent; |
|
struct child_latency_info *lat_info; |
|
struct latency_stat stat; |
|
unsigned long flags; |
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int cpu; |
|
|
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latency_stat_init(iolat, &stat); |
|
preempt_disable(); |
|
for_each_online_cpu(cpu) { |
|
struct latency_stat *s; |
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s = per_cpu_ptr(iolat->stats, cpu); |
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latency_stat_sum(iolat, &stat, s); |
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latency_stat_init(iolat, s); |
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} |
|
preempt_enable(); |
|
|
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parent = blkg_to_lat(blkg->parent); |
|
if (!parent) |
|
return; |
|
|
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lat_info = &parent->child_lat; |
|
|
|
iolat_update_total_lat_avg(iolat, &stat); |
|
|
|
/* Everything is ok and we don't need to adjust the scale. */ |
|
if (latency_sum_ok(iolat, &stat) && |
|
atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE) |
|
return; |
|
|
|
/* Somebody beat us to the punch, just bail. */ |
|
spin_lock_irqsave(&lat_info->lock, flags); |
|
|
|
latency_stat_sum(iolat, &iolat->cur_stat, &stat); |
|
lat_info->nr_samples -= iolat->nr_samples; |
|
lat_info->nr_samples += latency_stat_samples(iolat, &iolat->cur_stat); |
|
iolat->nr_samples = latency_stat_samples(iolat, &iolat->cur_stat); |
|
|
|
if ((lat_info->last_scale_event >= now || |
|
now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME)) |
|
goto out; |
|
|
|
if (latency_sum_ok(iolat, &iolat->cur_stat) && |
|
latency_sum_ok(iolat, &stat)) { |
|
if (latency_stat_samples(iolat, &iolat->cur_stat) < |
|
BLKIOLATENCY_MIN_GOOD_SAMPLES) |
|
goto out; |
|
if (lat_info->scale_grp == iolat) { |
|
lat_info->last_scale_event = now; |
|
scale_cookie_change(iolat->blkiolat, lat_info, true); |
|
} |
|
} else if (lat_info->scale_lat == 0 || |
|
lat_info->scale_lat >= iolat->min_lat_nsec) { |
|
lat_info->last_scale_event = now; |
|
if (!lat_info->scale_grp || |
|
lat_info->scale_lat > iolat->min_lat_nsec) { |
|
WRITE_ONCE(lat_info->scale_lat, iolat->min_lat_nsec); |
|
lat_info->scale_grp = iolat; |
|
} |
|
scale_cookie_change(iolat->blkiolat, lat_info, false); |
|
} |
|
latency_stat_init(iolat, &iolat->cur_stat); |
|
out: |
|
spin_unlock_irqrestore(&lat_info->lock, flags); |
|
} |
|
|
|
static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio) |
|
{ |
|
struct blkcg_gq *blkg; |
|
struct rq_wait *rqw; |
|
struct iolatency_grp *iolat; |
|
u64 window_start; |
|
u64 now; |
|
bool issue_as_root = bio_issue_as_root_blkg(bio); |
|
bool enabled = false; |
|
int inflight = 0; |
|
|
|
blkg = bio->bi_blkg; |
|
if (!blkg || !bio_flagged(bio, BIO_TRACKED)) |
|
return; |
|
|
|
iolat = blkg_to_lat(bio->bi_blkg); |
|
if (!iolat) |
|
return; |
|
|
|
enabled = blk_iolatency_enabled(iolat->blkiolat); |
|
if (!enabled) |
|
return; |
|
|
|
now = ktime_to_ns(ktime_get()); |
|
while (blkg && blkg->parent) { |
|
iolat = blkg_to_lat(blkg); |
|
if (!iolat) { |
|
blkg = blkg->parent; |
|
continue; |
|
} |
|
rqw = &iolat->rq_wait; |
|
|
|
inflight = atomic_dec_return(&rqw->inflight); |
|
WARN_ON_ONCE(inflight < 0); |
|
/* |
|
* If bi_status is BLK_STS_AGAIN, the bio wasn't actually |
|
* submitted, so do not account for it. |
|
*/ |
|
if (iolat->min_lat_nsec && bio->bi_status != BLK_STS_AGAIN) { |
|
iolatency_record_time(iolat, &bio->bi_issue, now, |
|
issue_as_root); |
|
window_start = atomic64_read(&iolat->window_start); |
|
if (now > window_start && |
|
(now - window_start) >= iolat->cur_win_nsec) { |
|
if (atomic64_cmpxchg(&iolat->window_start, |
|
window_start, now) == window_start) |
|
iolatency_check_latencies(iolat, now); |
|
} |
|
} |
|
wake_up(&rqw->wait); |
|
blkg = blkg->parent; |
|
} |
|
} |
|
|
|
static void blkcg_iolatency_exit(struct rq_qos *rqos) |
|
{ |
|
struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); |
|
|
|
del_timer_sync(&blkiolat->timer); |
|
blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency); |
|
kfree(blkiolat); |
|
} |
|
|
|
static struct rq_qos_ops blkcg_iolatency_ops = { |
|
.throttle = blkcg_iolatency_throttle, |
|
.done_bio = blkcg_iolatency_done_bio, |
|
.exit = blkcg_iolatency_exit, |
|
}; |
|
|
|
static void blkiolatency_timer_fn(struct timer_list *t) |
|
{ |
|
struct blk_iolatency *blkiolat = from_timer(blkiolat, t, timer); |
|
struct blkcg_gq *blkg; |
|
struct cgroup_subsys_state *pos_css; |
|
u64 now = ktime_to_ns(ktime_get()); |
|
|
|
rcu_read_lock(); |
|
blkg_for_each_descendant_pre(blkg, pos_css, |
|
blkiolat->rqos.q->root_blkg) { |
|
struct iolatency_grp *iolat; |
|
struct child_latency_info *lat_info; |
|
unsigned long flags; |
|
u64 cookie; |
|
|
|
/* |
|
* We could be exiting, don't access the pd unless we have a |
|
* ref on the blkg. |
|
*/ |
|
if (!blkg_tryget(blkg)) |
|
continue; |
|
|
|
iolat = blkg_to_lat(blkg); |
|
if (!iolat) |
|
goto next; |
|
|
|
lat_info = &iolat->child_lat; |
|
cookie = atomic_read(&lat_info->scale_cookie); |
|
|
|
if (cookie >= DEFAULT_SCALE_COOKIE) |
|
goto next; |
|
|
|
spin_lock_irqsave(&lat_info->lock, flags); |
|
if (lat_info->last_scale_event >= now) |
|
goto next_lock; |
|
|
|
/* |
|
* We scaled down but don't have a scale_grp, scale up and carry |
|
* on. |
|
*/ |
|
if (lat_info->scale_grp == NULL) { |
|
scale_cookie_change(iolat->blkiolat, lat_info, true); |
|
goto next_lock; |
|
} |
|
|
|
/* |
|
* It's been 5 seconds since our last scale event, clear the |
|
* scale grp in case the group that needed the scale down isn't |
|
* doing any IO currently. |
|
*/ |
|
if (now - lat_info->last_scale_event >= |
|
((u64)NSEC_PER_SEC * 5)) |
|
lat_info->scale_grp = NULL; |
|
next_lock: |
|
spin_unlock_irqrestore(&lat_info->lock, flags); |
|
next: |
|
blkg_put(blkg); |
|
} |
|
rcu_read_unlock(); |
|
} |
|
|
|
int blk_iolatency_init(struct request_queue *q) |
|
{ |
|
struct blk_iolatency *blkiolat; |
|
struct rq_qos *rqos; |
|
int ret; |
|
|
|
blkiolat = kzalloc(sizeof(*blkiolat), GFP_KERNEL); |
|
if (!blkiolat) |
|
return -ENOMEM; |
|
|
|
rqos = &blkiolat->rqos; |
|
rqos->id = RQ_QOS_LATENCY; |
|
rqos->ops = &blkcg_iolatency_ops; |
|
rqos->q = q; |
|
|
|
rq_qos_add(q, rqos); |
|
|
|
ret = blkcg_activate_policy(q, &blkcg_policy_iolatency); |
|
if (ret) { |
|
rq_qos_del(q, rqos); |
|
kfree(blkiolat); |
|
return ret; |
|
} |
|
|
|
timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0); |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* return 1 for enabling iolatency, return -1 for disabling iolatency, otherwise |
|
* return 0. |
|
*/ |
|
static int iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val) |
|
{ |
|
struct iolatency_grp *iolat = blkg_to_lat(blkg); |
|
u64 oldval = iolat->min_lat_nsec; |
|
|
|
iolat->min_lat_nsec = val; |
|
iolat->cur_win_nsec = max_t(u64, val << 4, BLKIOLATENCY_MIN_WIN_SIZE); |
|
iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec, |
|
BLKIOLATENCY_MAX_WIN_SIZE); |
|
|
|
if (!oldval && val) |
|
return 1; |
|
if (oldval && !val) { |
|
blkcg_clear_delay(blkg); |
|
return -1; |
|
} |
|
return 0; |
|
} |
|
|
|
static void iolatency_clear_scaling(struct blkcg_gq *blkg) |
|
{ |
|
if (blkg->parent) { |
|
struct iolatency_grp *iolat = blkg_to_lat(blkg->parent); |
|
struct child_latency_info *lat_info; |
|
if (!iolat) |
|
return; |
|
|
|
lat_info = &iolat->child_lat; |
|
spin_lock(&lat_info->lock); |
|
atomic_set(&lat_info->scale_cookie, DEFAULT_SCALE_COOKIE); |
|
lat_info->last_scale_event = 0; |
|
lat_info->scale_grp = NULL; |
|
lat_info->scale_lat = 0; |
|
spin_unlock(&lat_info->lock); |
|
} |
|
} |
|
|
|
static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, |
|
size_t nbytes, loff_t off) |
|
{ |
|
struct blkcg *blkcg = css_to_blkcg(of_css(of)); |
|
struct blkcg_gq *blkg; |
|
struct blkg_conf_ctx ctx; |
|
struct iolatency_grp *iolat; |
|
char *p, *tok; |
|
u64 lat_val = 0; |
|
u64 oldval; |
|
int ret; |
|
int enable = 0; |
|
|
|
ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx); |
|
if (ret) |
|
return ret; |
|
|
|
iolat = blkg_to_lat(ctx.blkg); |
|
p = ctx.body; |
|
|
|
ret = -EINVAL; |
|
while ((tok = strsep(&p, " "))) { |
|
char key[16]; |
|
char val[21]; /* 18446744073709551616 */ |
|
|
|
if (sscanf(tok, "%15[^=]=%20s", key, val) != 2) |
|
goto out; |
|
|
|
if (!strcmp(key, "target")) { |
|
u64 v; |
|
|
|
if (!strcmp(val, "max")) |
|
lat_val = 0; |
|
else if (sscanf(val, "%llu", &v) == 1) |
|
lat_val = v * NSEC_PER_USEC; |
|
else |
|
goto out; |
|
} else { |
|
goto out; |
|
} |
|
} |
|
|
|
/* Walk up the tree to see if our new val is lower than it should be. */ |
|
blkg = ctx.blkg; |
|
oldval = iolat->min_lat_nsec; |
|
|
|
enable = iolatency_set_min_lat_nsec(blkg, lat_val); |
|
if (enable) { |
|
if (!blk_get_queue(blkg->q)) { |
|
ret = -ENODEV; |
|
goto out; |
|
} |
|
|
|
blkg_get(blkg); |
|
} |
|
|
|
if (oldval != iolat->min_lat_nsec) { |
|
iolatency_clear_scaling(blkg); |
|
} |
|
|
|
ret = 0; |
|
out: |
|
blkg_conf_finish(&ctx); |
|
if (ret == 0 && enable) { |
|
struct iolatency_grp *tmp = blkg_to_lat(blkg); |
|
struct blk_iolatency *blkiolat = tmp->blkiolat; |
|
|
|
blk_mq_freeze_queue(blkg->q); |
|
|
|
if (enable == 1) |
|
atomic_inc(&blkiolat->enabled); |
|
else if (enable == -1) |
|
atomic_dec(&blkiolat->enabled); |
|
else |
|
WARN_ON_ONCE(1); |
|
|
|
blk_mq_unfreeze_queue(blkg->q); |
|
|
|
blkg_put(blkg); |
|
blk_put_queue(blkg->q); |
|
} |
|
return ret ?: nbytes; |
|
} |
|
|
|
static u64 iolatency_prfill_limit(struct seq_file *sf, |
|
struct blkg_policy_data *pd, int off) |
|
{ |
|
struct iolatency_grp *iolat = pd_to_lat(pd); |
|
const char *dname = blkg_dev_name(pd->blkg); |
|
|
|
if (!dname || !iolat->min_lat_nsec) |
|
return 0; |
|
seq_printf(sf, "%s target=%llu\n", |
|
dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC)); |
|
return 0; |
|
} |
|
|
|
static int iolatency_print_limit(struct seq_file *sf, void *v) |
|
{ |
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), |
|
iolatency_prfill_limit, |
|
&blkcg_policy_iolatency, seq_cft(sf)->private, false); |
|
return 0; |
|
} |
|
|
|
static bool iolatency_ssd_stat(struct iolatency_grp *iolat, struct seq_file *s) |
|
{ |
|
struct latency_stat stat; |
|
int cpu; |
|
|
|
latency_stat_init(iolat, &stat); |
|
preempt_disable(); |
|
for_each_online_cpu(cpu) { |
|
struct latency_stat *s; |
|
s = per_cpu_ptr(iolat->stats, cpu); |
|
latency_stat_sum(iolat, &stat, s); |
|
} |
|
preempt_enable(); |
|
|
|
if (iolat->rq_depth.max_depth == UINT_MAX) |
|
seq_printf(s, " missed=%llu total=%llu depth=max", |
|
(unsigned long long)stat.ps.missed, |
|
(unsigned long long)stat.ps.total); |
|
else |
|
seq_printf(s, " missed=%llu total=%llu depth=%u", |
|
(unsigned long long)stat.ps.missed, |
|
(unsigned long long)stat.ps.total, |
|
iolat->rq_depth.max_depth); |
|
return true; |
|
} |
|
|
|
static bool iolatency_pd_stat(struct blkg_policy_data *pd, struct seq_file *s) |
|
{ |
|
struct iolatency_grp *iolat = pd_to_lat(pd); |
|
unsigned long long avg_lat; |
|
unsigned long long cur_win; |
|
|
|
if (!blkcg_debug_stats) |
|
return false; |
|
|
|
if (iolat->ssd) |
|
return iolatency_ssd_stat(iolat, s); |
|
|
|
avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC); |
|
cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC); |
|
if (iolat->rq_depth.max_depth == UINT_MAX) |
|
seq_printf(s, " depth=max avg_lat=%llu win=%llu", |
|
avg_lat, cur_win); |
|
else |
|
seq_printf(s, " depth=%u avg_lat=%llu win=%llu", |
|
iolat->rq_depth.max_depth, avg_lat, cur_win); |
|
return true; |
|
} |
|
|
|
static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, |
|
struct request_queue *q, |
|
struct blkcg *blkcg) |
|
{ |
|
struct iolatency_grp *iolat; |
|
|
|
iolat = kzalloc_node(sizeof(*iolat), gfp, q->node); |
|
if (!iolat) |
|
return NULL; |
|
iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat), |
|
__alignof__(struct latency_stat), gfp); |
|
if (!iolat->stats) { |
|
kfree(iolat); |
|
return NULL; |
|
} |
|
return &iolat->pd; |
|
} |
|
|
|
static void iolatency_pd_init(struct blkg_policy_data *pd) |
|
{ |
|
struct iolatency_grp *iolat = pd_to_lat(pd); |
|
struct blkcg_gq *blkg = lat_to_blkg(iolat); |
|
struct rq_qos *rqos = blkcg_rq_qos(blkg->q); |
|
struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); |
|
u64 now = ktime_to_ns(ktime_get()); |
|
int cpu; |
|
|
|
if (blk_queue_nonrot(blkg->q)) |
|
iolat->ssd = true; |
|
else |
|
iolat->ssd = false; |
|
|
|
for_each_possible_cpu(cpu) { |
|
struct latency_stat *stat; |
|
stat = per_cpu_ptr(iolat->stats, cpu); |
|
latency_stat_init(iolat, stat); |
|
} |
|
|
|
latency_stat_init(iolat, &iolat->cur_stat); |
|
rq_wait_init(&iolat->rq_wait); |
|
spin_lock_init(&iolat->child_lat.lock); |
|
iolat->rq_depth.queue_depth = blkg->q->nr_requests; |
|
iolat->rq_depth.max_depth = UINT_MAX; |
|
iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth; |
|
iolat->blkiolat = blkiolat; |
|
iolat->cur_win_nsec = 100 * NSEC_PER_MSEC; |
|
atomic64_set(&iolat->window_start, now); |
|
|
|
/* |
|
* We init things in list order, so the pd for the parent may not be |
|
* init'ed yet for whatever reason. |
|
*/ |
|
if (blkg->parent && blkg_to_pd(blkg->parent, &blkcg_policy_iolatency)) { |
|
struct iolatency_grp *parent = blkg_to_lat(blkg->parent); |
|
atomic_set(&iolat->scale_cookie, |
|
atomic_read(&parent->child_lat.scale_cookie)); |
|
} else { |
|
atomic_set(&iolat->scale_cookie, DEFAULT_SCALE_COOKIE); |
|
} |
|
|
|
atomic_set(&iolat->child_lat.scale_cookie, DEFAULT_SCALE_COOKIE); |
|
} |
|
|
|
static void iolatency_pd_offline(struct blkg_policy_data *pd) |
|
{ |
|
struct iolatency_grp *iolat = pd_to_lat(pd); |
|
struct blkcg_gq *blkg = lat_to_blkg(iolat); |
|
struct blk_iolatency *blkiolat = iolat->blkiolat; |
|
int ret; |
|
|
|
ret = iolatency_set_min_lat_nsec(blkg, 0); |
|
if (ret == 1) |
|
atomic_inc(&blkiolat->enabled); |
|
if (ret == -1) |
|
atomic_dec(&blkiolat->enabled); |
|
iolatency_clear_scaling(blkg); |
|
} |
|
|
|
static void iolatency_pd_free(struct blkg_policy_data *pd) |
|
{ |
|
struct iolatency_grp *iolat = pd_to_lat(pd); |
|
free_percpu(iolat->stats); |
|
kfree(iolat); |
|
} |
|
|
|
static struct cftype iolatency_files[] = { |
|
{ |
|
.name = "latency", |
|
.flags = CFTYPE_NOT_ON_ROOT, |
|
.seq_show = iolatency_print_limit, |
|
.write = iolatency_set_limit, |
|
}, |
|
{} |
|
}; |
|
|
|
static struct blkcg_policy blkcg_policy_iolatency = { |
|
.dfl_cftypes = iolatency_files, |
|
.pd_alloc_fn = iolatency_pd_alloc, |
|
.pd_init_fn = iolatency_pd_init, |
|
.pd_offline_fn = iolatency_pd_offline, |
|
.pd_free_fn = iolatency_pd_free, |
|
.pd_stat_fn = iolatency_pd_stat, |
|
}; |
|
|
|
static int __init iolatency_init(void) |
|
{ |
|
return blkcg_policy_register(&blkcg_policy_iolatency); |
|
} |
|
|
|
static void __exit iolatency_exit(void) |
|
{ |
|
blkcg_policy_unregister(&blkcg_policy_iolatency); |
|
} |
|
|
|
module_init(iolatency_init); |
|
module_exit(iolatency_exit);
|
|
|