| /* |
| * Block rq-qos base io controller |
| * |
| * This works similar to wbt with a few exceptions |
| * |
| * - It's bio based, so the latency covers the whole block layer in addition to |
| * the actual io. |
| * - We will throttle all IO that comes in here if we need to. |
| * - We use the mean latency over the 100ms window. This is because writes can |
| * be particularly fast, which could give us a false sense of the impact of |
| * other workloads on our protected workload. |
| * - By default there's no throttling, we set the queue_depth to INT_MAX so that |
| * we can have as many outstanding bio's as we're allowed to. Only at |
| * throttle time do we pay attention to the actual queue depth. |
| * |
| * The hierarchy works like the cpu controller does, we track the latency at |
| * every configured node, and each configured node has it's own independent |
| * queue depth. This means that we only care about our latency targets at the |
| * peer level. Some group at the bottom of the hierarchy isn't going to affect |
| * a group at the end of some other path if we're only configred at leaf level. |
| * |
| * Consider the following |
| * |
| * root blkg |
| * / \ |
| * fast (target=5ms) slow (target=10ms) |
| * / \ / \ |
| * a b normal(15ms) unloved |
| * |
| * "a" and "b" have no target, but their combined io under "fast" cannot exceed |
| * an average latency of 5ms. If it does then we will throttle the "slow" |
| * group. In the case of "normal", if it exceeds its 15ms target, we will |
| * throttle "unloved", but nobody else. |
| * |
| * In this example "fast", "slow", and "normal" will be the only groups actually |
| * accounting their io latencies. We have to walk up the heirarchy to the root |
| * on every submit and complete so we can do the appropriate stat recording and |
| * adjust the queue depth of ourselves if needed. |
| * |
| * There are 2 ways we throttle IO. |
| * |
| * 1) Queue depth throttling. As we throttle down we will adjust the maximum |
| * number of IO's we're allowed to have in flight. This starts at (u64)-1 down |
| * to 1. If the group is only ever submitting IO for itself then this is the |
| * only way we throttle. |
| * |
| * 2) Induced delay throttling. This is for the case that a group is generating |
| * IO that has to be issued by the root cg to avoid priority inversion. So think |
| * REQ_META or REQ_SWAP. If we are already at qd == 1 and we're getting a lot |
| * of work done for us on behalf of the root cg and are being asked to scale |
| * down more then we induce a latency at userspace return. We accumulate the |
| * total amount of time we need to be punished by doing |
| * |
| * total_time += min_lat_nsec - actual_io_completion |
| * |
| * and then at throttle time will do |
| * |
| * throttle_time = min(total_time, NSEC_PER_SEC) |
| * |
| * This induced delay will throttle back the activity that is generating the |
| * root cg issued io's, wethere that's some metadata intensive operation or the |
| * group is using so much memory that it is pushing us into swap. |
| * |
| * Copyright (C) 2018 Josef Bacik |
| */ |
| #include <linux/kernel.h> |
| #include <linux/blk_types.h> |
| #include <linux/backing-dev.h> |
| #include <linux/module.h> |
| #include <linux/timer.h> |
| #include <linux/memcontrol.h> |
| #include <trace/events/block.h> |
| #include "blk-wbt.h" |
| |
| #define DEFAULT_SCALE_COOKIE 1000000U |
| |
| static struct blkcg_policy blkcg_policy_iolatency; |
| struct iolatency_grp; |
| |
| struct blk_iolatency { |
| struct rq_qos rqos; |
| struct timer_list timer; |
| atomic_t enabled; |
| }; |
| |
| static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos) |
| { |
| return container_of(rqos, struct blk_iolatency, rqos); |
| } |
| |
| static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat) |
| { |
| return atomic_read(&blkiolat->enabled) > 0; |
| } |
| |
| struct child_latency_info { |
| spinlock_t lock; |
| |
| /* Last time we adjusted the scale of everybody. */ |
| u64 last_scale_event; |
| |
| /* The latency that we missed. */ |
| u64 scale_lat; |
| |
| /* The guy who actually changed the latency numbers. */ |
| struct iolatency_grp *scale_grp; |
| |
| /* Cookie to tell if we need to scale up or down. */ |
| atomic_t scale_cookie; |
| }; |
| |
| struct iolatency_grp { |
| struct blkg_policy_data pd; |
| struct blk_rq_stat __percpu *stats; |
| struct blk_iolatency *blkiolat; |
| struct rq_depth rq_depth; |
| struct rq_wait rq_wait; |
| atomic64_t window_start; |
| atomic_t scale_cookie; |
| u64 min_lat_nsec; |
| u64 cur_win_nsec; |
| |
| /* total running average of our io latency. */ |
| u64 total_lat_avg; |
| u64 total_lat_nr; |
| |
| struct child_latency_info child_lat; |
| }; |
| |
| static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd) |
| { |
| return container_of(pd, struct iolatency_grp, pd); |
| } |
| |
| static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg) |
| { |
| return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency)); |
| } |
| |
| static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat) |
| { |
| return pd_to_blkg(&iolat->pd); |
| } |
| |
| static inline bool iolatency_may_queue(struct iolatency_grp *iolat, |
| wait_queue_entry_t *wait) |
| { |
| struct rq_wait *rqw = &iolat->rq_wait; |
| |
| if (waitqueue_active(&rqw->wait) && |
| rqw->wait.head.next != &wait->entry) |
| return false; |
| return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth); |
| } |
| |
| static void __blkcg_iolatency_throttle(struct rq_qos *rqos, |
| struct iolatency_grp *iolat, |
| spinlock_t *lock, bool issue_as_root, |
| bool use_memdelay) |
| __releases(lock) |
| __acquires(lock) |
| { |
| struct rq_wait *rqw = &iolat->rq_wait; |
| unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay); |
| DEFINE_WAIT(wait); |
| |
| if (use_delay) |
| blkcg_schedule_throttle(rqos->q, use_memdelay); |
| |
| /* We don't wait for a qd slot, we just take what we want. */ |
| if (issue_as_root) { |
| atomic_inc(&rqw->inflight); |
| return; |
| } |
| |
| if (iolatency_may_queue(iolat, &wait)) |
| return; |
| |
| do { |
| prepare_to_wait_exclusive(&rqw->wait, &wait, |
| TASK_UNINTERRUPTIBLE); |
| if (iolatency_may_queue(iolat, &wait)) |
| break; |
| |
| if (lock) { |
| spin_unlock_irq(lock); |
| io_schedule(); |
| spin_lock_irq(lock); |
| } else { |
| io_schedule(); |
| } |
| } while (1); |
| |
| finish_wait(&rqw->wait, &wait); |
| } |
| |
| #define SCALE_DOWN_FACTOR 2 |
| #define SCALE_UP_FACTOR 4 |
| |
| static inline unsigned long scale_amount(unsigned long qd, bool up) |
| { |
| return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL); |
| } |
| |
| /* |
| * We scale the qd down faster than we scale up, so we need to use this helper |
| * to adjust the scale_cookie accordingly so we don't prematurely get |
| * scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much. |
| */ |
| static void scale_cookie_change(struct blk_iolatency *blkiolat, |
| struct child_latency_info *lat_info, |
| bool up) |
| { |
| unsigned long qd = blk_queue_depth(blkiolat->rqos.q); |
| unsigned long scale = scale_amount(qd, up); |
| unsigned long old = atomic_read(&lat_info->scale_cookie); |
| |
| if (up) { |
| if (scale + old > DEFAULT_SCALE_COOKIE) |
| atomic_set(&lat_info->scale_cookie, |
| DEFAULT_SCALE_COOKIE); |
| else if (DEFAULT_SCALE_COOKIE - old > qd) |
| atomic_inc(&lat_info->scale_cookie); |
| else |
| atomic_add(scale, &lat_info->scale_cookie); |
| } else { |
| if (DEFAULT_SCALE_COOKIE - old > qd) |
| atomic_dec(&lat_info->scale_cookie); |
| else |
| atomic_sub(scale, &lat_info->scale_cookie); |
| } |
| } |
| |
| /* |
| * Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the |
| * queue depth at a time so we don't get wild swings and hopefully dial in to |
| * fairer distribution of the overall queue depth. |
| */ |
| static void scale_change(struct iolatency_grp *iolat, bool up) |
| { |
| unsigned long qd = blk_queue_depth(iolat->blkiolat->rqos.q); |
| unsigned long scale = scale_amount(qd, up); |
| unsigned long old = iolat->rq_depth.max_depth; |
| bool changed = false; |
| |
| if (old > qd) |
| old = qd; |
| |
| if (up) { |
| if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat))) |
| return; |
| |
| if (old < qd) { |
| changed = true; |
| old += scale; |
| old = min(old, qd); |
| iolat->rq_depth.max_depth = old; |
| wake_up_all(&iolat->rq_wait.wait); |
| } |
| } else if (old > 1) { |
| old >>= 1; |
| changed = true; |
| iolat->rq_depth.max_depth = max(old, 1UL); |
| } |
| } |
| |
| /* Check our parent and see if the scale cookie has changed. */ |
| static void check_scale_change(struct iolatency_grp *iolat) |
| { |
| struct iolatency_grp *parent; |
| struct child_latency_info *lat_info; |
| unsigned int cur_cookie; |
| unsigned int our_cookie = atomic_read(&iolat->scale_cookie); |
| u64 scale_lat; |
| unsigned int old; |
| int direction = 0; |
| |
| if (lat_to_blkg(iolat)->parent == NULL) |
| return; |
| |
| parent = blkg_to_lat(lat_to_blkg(iolat)->parent); |
| lat_info = &parent->child_lat; |
| cur_cookie = atomic_read(&lat_info->scale_cookie); |
| scale_lat = READ_ONCE(lat_info->scale_lat); |
| |
| if (cur_cookie < our_cookie) |
| direction = -1; |
| else if (cur_cookie > our_cookie) |
| direction = 1; |
| else |
| return; |
| |
| old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie); |
| |
| /* Somebody beat us to the punch, just bail. */ |
| if (old != our_cookie) |
| return; |
| |
| if (direction < 0 && (!scale_lat || iolat->min_lat_nsec <= scale_lat)) |
| return; |
| |
| /* We're as low as we can go. */ |
| if (iolat->rq_depth.max_depth == 1 && direction < 0) { |
| blkcg_use_delay(lat_to_blkg(iolat)); |
| return; |
| } |
| |
| /* We're back to the default cookie, unthrottle all the things. */ |
| if (cur_cookie == DEFAULT_SCALE_COOKIE) { |
| blkcg_clear_delay(lat_to_blkg(iolat)); |
| iolat->rq_depth.max_depth = INT_MAX; |
| wake_up_all(&iolat->rq_wait.wait); |
| return; |
| } |
| |
| scale_change(iolat, direction > 0); |
| } |
| |
| static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio, |
| spinlock_t *lock) |
| { |
| struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); |
| struct blkcg *blkcg; |
| struct blkcg_gq *blkg; |
| struct request_queue *q = rqos->q; |
| bool issue_as_root = bio_issue_as_root_blkg(bio); |
| |
| if (!blk_iolatency_enabled(blkiolat)) |
| return; |
| |
| rcu_read_lock(); |
| blkcg = bio_blkcg(bio); |
| bio_associate_blkcg(bio, &blkcg->css); |
| blkg = blkg_lookup(blkcg, q); |
| if (unlikely(!blkg)) { |
| if (!lock) |
| spin_lock_irq(q->queue_lock); |
| blkg = blkg_lookup_create(blkcg, q); |
| if (IS_ERR(blkg)) |
| blkg = NULL; |
| if (!lock) |
| spin_unlock_irq(q->queue_lock); |
| } |
| if (!blkg) |
| goto out; |
| |
| bio_issue_init(&bio->bi_issue, bio_sectors(bio)); |
| bio_associate_blkg(bio, blkg); |
| out: |
| rcu_read_unlock(); |
| while (blkg && blkg->parent) { |
| struct iolatency_grp *iolat = blkg_to_lat(blkg); |
| |
| check_scale_change(iolat); |
| __blkcg_iolatency_throttle(rqos, iolat, lock, issue_as_root, |
| (bio->bi_opf & REQ_SWAP) == REQ_SWAP); |
| blkg = blkg->parent; |
| } |
| if (!timer_pending(&blkiolat->timer)) |
| mod_timer(&blkiolat->timer, jiffies + HZ); |
| } |
| |
| static void iolatency_record_time(struct iolatency_grp *iolat, |
| struct bio_issue *issue, u64 now, |
| bool issue_as_root) |
| { |
| struct blk_rq_stat *rq_stat; |
| u64 start = bio_issue_time(issue); |
| u64 req_time; |
| |
| if (now <= start) |
| return; |
| |
| 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 != (u64)-1)) { |
| u64 sub = iolat->min_lat_nsec; |
| if (req_time < sub) |
| blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time); |
| return; |
| } |
| |
| rq_stat = get_cpu_ptr(iolat->stats); |
| blk_rq_stat_add(rq_stat, req_time); |
| put_cpu_ptr(rq_stat); |
| } |
| |
| #define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC) |
| #define BLKIOLATENCY_MIN_GOOD_SAMPLES 5 |
| |
| 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 blk_rq_stat stat; |
| unsigned long flags; |
| int cpu; |
| |
| blk_rq_stat_init(&stat); |
| preempt_disable(); |
| for_each_online_cpu(cpu) { |
| struct blk_rq_stat *s; |
| s = per_cpu_ptr(iolat->stats, cpu); |
| blk_rq_stat_sum(&stat, s); |
| blk_rq_stat_init(s); |
| } |
| preempt_enable(); |
| |
| /* |
| * Our average exceeded our window, scale up our window so we are more |
| * accurate, but not more than the global timer. |
| */ |
| if (stat.mean > iolat->cur_win_nsec) { |
| iolat->cur_win_nsec <<= 1; |
| iolat->cur_win_nsec = |
| max_t(u64, iolat->cur_win_nsec, NSEC_PER_SEC); |
| } |
| |
| if (!blkg->parent) |
| return; |
| |
| parent = blkg_to_lat(blkg->parent); |
| lat_info = &parent->child_lat; |
| |
| iolat->total_lat_avg = |
| div64_u64((iolat->total_lat_avg * iolat->total_lat_nr) + |
| stat.mean, iolat->total_lat_nr + 1); |
| |
| iolat->total_lat_nr++; |
| |
| /* Everything is ok and we don't need to adjust the scale. */ |
| if (stat.mean <= iolat->min_lat_nsec && |
| 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); |
| if ((lat_info->last_scale_event >= now || |
| now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME) && |
| lat_info->scale_lat <= iolat->min_lat_nsec) |
| goto out; |
| |
| if (stat.mean <= iolat->min_lat_nsec && |
| stat.nr_samples >= BLKIOLATENCY_MIN_GOOD_SAMPLES) { |
| lat_info->last_scale_event = now; |
| if (lat_info->scale_grp == iolat) |
| scale_cookie_change(iolat->blkiolat, lat_info, true); |
| } else if (stat.mean > 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); |
| } |
| 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 = ktime_to_ns(ktime_get()); |
| bool issue_as_root = bio_issue_as_root_blkg(bio); |
| bool enabled = false; |
| |
| blkg = bio->bi_blkg; |
| if (!blkg) |
| return; |
| |
| iolat = blkg_to_lat(blkg); |
| enabled = blk_iolatency_enabled(iolat->blkiolat); |
| |
| while (blkg->parent) { |
| iolat = blkg_to_lat(blkg); |
| rqw = &iolat->rq_wait; |
| |
| atomic_dec(&rqw->inflight); |
| if (!enabled || iolat->min_lat_nsec == 0) |
| goto next; |
| 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); |
| } |
| next: |
| wake_up_all(&rqw->wait); |
| blkg = blkg->parent; |
| } |
| } |
| |
| static void blkcg_iolatency_cleanup(struct rq_qos *rqos, struct bio *bio) |
| { |
| struct blkcg_gq *blkg; |
| |
| blkg = bio->bi_blkg; |
| while (blkg && blkg->parent) { |
| struct rq_wait *rqw; |
| struct iolatency_grp *iolat; |
| |
| iolat = blkg_to_lat(blkg); |
| rqw = &iolat->rq_wait; |
| |
| atomic_dec(&rqw->inflight); |
| wake_up_all(&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, |
| .cleanup = blkcg_iolatency_cleanup, |
| .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 = blkg_to_lat(blkg); |
| struct child_latency_info *lat_info = &iolat->child_lat; |
| unsigned long flags; |
| u64 cookie = atomic_read(&lat_info->scale_cookie); |
| |
| if (cookie >= DEFAULT_SCALE_COOKIE) |
| continue; |
| |
| spin_lock_irqsave(&lat_info->lock, flags); |
| if (lat_info->last_scale_event >= now) |
| goto next; |
| |
| /* |
| * 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; |
| } |
| |
| /* |
| * 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: |
| spin_unlock_irqrestore(&lat_info->lock, flags); |
| } |
| 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_CGROUP; |
| rqos->ops = &blkcg_iolatency_ops; |
| rqos->q = q; |
| |
| rq_qos_add(q, rqos); |
| |
| ret = blkcg_activate_policy(q, &blkcg_policy_iolatency); |
| if (ret) { |
| kfree(blkiolat); |
| return ret; |
| } |
| |
| timer_setup(&blkiolat->timer, blkiolatency_timer_fn, |
| (unsigned long)blkiolat); |
| |
| return 0; |
| } |
| |
| static void iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val) |
| { |
| struct iolatency_grp *iolat = blkg_to_lat(blkg); |
| struct blk_iolatency *blkiolat = iolat->blkiolat; |
| u64 oldval = iolat->min_lat_nsec; |
| |
| iolat->min_lat_nsec = val; |
| iolat->cur_win_nsec = max_t(u64, val << 4, 100 * NSEC_PER_MSEC); |
| iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec, NSEC_PER_SEC); |
| |
| if (!oldval && val) |
| atomic_inc(&blkiolat->enabled); |
| if (oldval && !val) |
| atomic_dec(&blkiolat->enabled); |
| } |
| |
| 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 = &iolat->child_lat; |
| |
| spin_lock_irq(&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_irq(&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 blk_iolatency *blkiolat; |
| struct blkg_conf_ctx ctx; |
| struct iolatency_grp *iolat; |
| char *p, *tok; |
| u64 lat_val = 0; |
| u64 oldval; |
| int ret; |
| |
| ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx); |
| if (ret) |
| return ret; |
| |
| iolat = blkg_to_lat(ctx.blkg); |
| blkiolat = iolat->blkiolat; |
| 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; |
| |
| iolatency_set_min_lat_nsec(blkg, lat_val); |
| if (oldval != iolat->min_lat_nsec) |
| iolatency_clear_scaling(blkg); |
| |
| ret = 0; |
| out: |
| blkg_conf_finish(&ctx); |
| 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, |
| (unsigned long long)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 size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf, |
| size_t size) |
| { |
| struct iolatency_grp *iolat = pd_to_lat(pd); |
| unsigned long long avg_lat = div64_u64(iolat->total_lat_avg, NSEC_PER_USEC); |
| |
| if (!iolat->min_lat_nsec) |
| return 0; |
| |
| if (iolat->rq_depth.max_depth == (u64)-1) |
| return scnprintf(buf, size, " depth=max avg_lat=%llu", |
| avg_lat); |
| |
| return scnprintf(buf, size, " depth=%u avg_lat=%llu", |
| iolat->rq_depth.max_depth, avg_lat); |
| } |
| |
| |
| static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, int node) |
| { |
| struct iolatency_grp *iolat; |
| |
| iolat = kzalloc_node(sizeof(*iolat), gfp, node); |
| if (!iolat) |
| return NULL; |
| iolat->stats = __alloc_percpu_gfp(sizeof(struct blk_rq_stat), |
| __alignof__(struct blk_rq_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; |
| |
| for_each_possible_cpu(cpu) { |
| struct blk_rq_stat *stat; |
| stat = per_cpu_ptr(iolat->stats, cpu); |
| blk_rq_stat_init(stat); |
| } |
| |
| rq_wait_init(&iolat->rq_wait); |
| spin_lock_init(&iolat->child_lat.lock); |
| iolat->rq_depth.queue_depth = blk_queue_depth(blkg->q); |
| iolat->rq_depth.max_depth = INT_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); |
| |
| iolatency_set_min_lat_nsec(blkg, 0); |
| 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) |
| { |
| return blkcg_policy_unregister(&blkcg_policy_iolatency); |
| } |
| |
| module_init(iolatency_init); |
| module_exit(iolatency_exit); |