--- /dev/null
+/*
+ * 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 <linux/sched/signal.h>
+#include <trace/events/block.h>
+#include "blk-rq-qos.h"
+#include "blk-stat.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;
+
+ /* Total io's from all of our children for the last summation. */
+ u64 nr_samples;
+
+ /* 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;
+
+ /* Our current number of IO's for the last summation. */
+ u64 nr_samples;
+
+ struct child_latency_info child_lat;
+};
+
+static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd)
+{
+ return pd ? container_of(pd, struct iolatency_grp, pd) : NULL;
+}
+
+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,
+ bool first_block)
+{
+ struct rq_wait *rqw = &iolat->rq_wait;
+
+ if (first_block && 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);
+ bool first_block = true;
+
+ if (use_delay)
+ blkcg_schedule_throttle(rqos->q, use_memdelay);
+
+ /*
+ * To avoid priority inversions we want to just take a slot if we are
+ * issuing as root. If we're being killed off there's no point in
+ * delaying things, we may have been killed by OOM so throttling may
+ * make recovery take even longer, so just let the IO's through so the
+ * task can go away.
+ */
+ if (issue_as_root || fatal_signal_pending(current)) {
+ atomic_inc(&rqw->inflight);
+ return;
+ }
+
+ if (iolatency_may_queue(iolat, &wait, first_block))
+ return;
+
+ do {
+ prepare_to_wait_exclusive(&rqw->wait, &wait,
+ TASK_UNINTERRUPTIBLE);
+
+ if (iolatency_may_queue(iolat, &wait, first_block))
+ break;
+ first_block = false;
+
+ 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.
+ *
+ * Each group has their own local copy of the last scale cookie they saw, so if
+ * the global scale cookie goes up or down they know which way they need to go
+ * based on their last knowledge of it.
+ */
+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);
+ unsigned long max_scale = qd << 1;
+ unsigned long diff = 0;
+
+ if (old < DEFAULT_SCALE_COOKIE)
+ diff = DEFAULT_SCALE_COOKIE - old;
+
+ if (up) {
+ if (scale + old > DEFAULT_SCALE_COOKIE)
+ atomic_set(&lat_info->scale_cookie,
+ DEFAULT_SCALE_COOKIE);
+ else if (diff > qd)
+ atomic_inc(&lat_info->scale_cookie);
+ else
+ atomic_add(scale, &lat_info->scale_cookie);
+ } else {
+ /*
+ * We don't want to dig a hole so deep that it takes us hours to
+ * dig out of it. Just enough that we don't throttle/unthrottle
+ * with jagged workloads but can still unthrottle once pressure
+ * has sufficiently dissipated.
+ */
+ if (diff > qd) {
+ if (diff < max_scale)
+ 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);
+ if (!parent)
+ return;
+
+ 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 && iolat->min_lat_nsec) {
+ u64 samples_thresh;
+
+ if (!scale_lat || iolat->min_lat_nsec <= scale_lat)
+ return;
+
+ /*
+ * Sometimes high priority groups are their own worst enemy, so
+ * instead of taking it out on some poor other group that did 5%
+ * or less of the IO's for the last summation just skip this
+ * scale down event.
+ */
+ samples_thresh = lat_info->nr_samples * 5;
+ samples_thresh = div64_u64(samples_thresh, 100);
+ if (iolat->nr_samples <= samples_thresh)
+ 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);
+ if (!iolat) {
+ blkg = blkg->parent;
+ continue;
+ }
+
+ 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);
+ }
+
+ parent = blkg_to_lat(blkg->parent);
+ if (!parent)
+ return;
+
+ 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);
+ lat_info->nr_samples -= iolat->nr_samples;
+ lat_info->nr_samples += stat.nr_samples;
+ iolat->nr_samples = stat.nr_samples;
+
+ 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) {
+ if (lat_info->scale_grp == iolat) {
+ lat_info->last_scale_event = now;
+ 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(bio->bi_blkg);
+ if (!iolat)
+ return;
+
+ enabled = blk_iolatency_enabled(iolat->blkiolat);
+ while (blkg && blkg->parent) {
+ iolat = blkg_to_lat(blkg);
+ if (!iolat) {
+ blkg = blkg->parent;
+ continue;
+ }
+ 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(&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);
+ if (!iolat)
+ goto next;
+
+ rqw = &iolat->rq_wait;
+ atomic_dec(&rqw->inflight);
+ wake_up(&rqw->wait);
+next:
+ 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;
+ 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_try_get(blkg))
+ continue;
+
+ iolat = blkg_to_lat(blkg);
+ if (!iolat)
+ continue;
+
+ 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_CGROUP;
+ 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;
+}
+
+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;
+ 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 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->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);
projects / openwrt / staging / blogic.git / commitdiff