blk-throttle: add downgrade logic
When queue state machine is in LIMIT_MAX state, but a cgroup is below its low limit for some time, the queue should be downgraded to lower state as one cgroup's low limit isn't met. Signed-off-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Shaohua Li
Jens Axboe
parent
c79892c557
commit
3f0abd8066
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@ -140,6 +140,13 @@ struct throtl_grp {
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/* Number of bio's dispatched in current slice */
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unsigned int io_disp[2];
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unsigned long last_low_overflow_time[2];
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uint64_t last_bytes_disp[2];
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unsigned int last_io_disp[2];
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unsigned long last_check_time;
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/* When did we start a new slice */
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unsigned long slice_start[2];
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unsigned long slice_end[2];
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@ -159,6 +166,9 @@ struct throtl_data
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struct work_struct dispatch_work;
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unsigned int limit_index;
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bool limit_valid[LIMIT_CNT];
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unsigned long low_upgrade_time;
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unsigned long low_downgrade_time;
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};
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static void throtl_pending_timer_fn(unsigned long arg);
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@ -898,6 +908,8 @@ static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
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/* Charge the bio to the group */
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tg->bytes_disp[rw] += bio->bi_iter.bi_size;
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tg->io_disp[rw]++;
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tg->last_bytes_disp[rw] += bio->bi_iter.bi_size;
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tg->last_io_disp[rw]++;
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/*
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* BIO_THROTTLED is used to prevent the same bio to be throttled
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@ -1527,6 +1539,45 @@ static struct blkcg_policy blkcg_policy_throtl = {
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.pd_free_fn = throtl_pd_free,
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};
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static unsigned long __tg_last_low_overflow_time(struct throtl_grp *tg)
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{
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unsigned long rtime = jiffies, wtime = jiffies;
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if (tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW])
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rtime = tg->last_low_overflow_time[READ];
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if (tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
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wtime = tg->last_low_overflow_time[WRITE];
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return min(rtime, wtime);
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}
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/* tg should not be an intermediate node */
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static unsigned long tg_last_low_overflow_time(struct throtl_grp *tg)
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{
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struct throtl_service_queue *parent_sq;
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struct throtl_grp *parent = tg;
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unsigned long ret = __tg_last_low_overflow_time(tg);
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while (true) {
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parent_sq = parent->service_queue.parent_sq;
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parent = sq_to_tg(parent_sq);
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if (!parent)
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break;
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/*
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* The parent doesn't have low limit, it always reaches low
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* limit. Its overflow time is useless for children
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*/
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if (!parent->bps[READ][LIMIT_LOW] &&
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!parent->iops[READ][LIMIT_LOW] &&
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!parent->bps[WRITE][LIMIT_LOW] &&
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!parent->iops[WRITE][LIMIT_LOW])
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continue;
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if (time_after(__tg_last_low_overflow_time(parent), ret))
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ret = __tg_last_low_overflow_time(parent);
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}
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return ret;
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}
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static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
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{
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struct throtl_service_queue *sq = &tg->service_queue;
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@ -1570,6 +1621,9 @@ static bool throtl_can_upgrade(struct throtl_data *td,
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if (td->limit_index != LIMIT_LOW)
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return false;
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if (time_before(jiffies, td->low_downgrade_time + throtl_slice))
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return false;
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rcu_read_lock();
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blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
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struct throtl_grp *tg = blkg_to_tg(blkg);
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@ -1593,6 +1647,7 @@ static void throtl_upgrade_state(struct throtl_data *td)
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struct blkcg_gq *blkg;
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td->limit_index = LIMIT_MAX;
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td->low_upgrade_time = jiffies;
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rcu_read_lock();
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blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
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struct throtl_grp *tg = blkg_to_tg(blkg);
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@ -1608,6 +1663,99 @@ static void throtl_upgrade_state(struct throtl_data *td)
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queue_work(kthrotld_workqueue, &td->dispatch_work);
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}
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static void throtl_downgrade_state(struct throtl_data *td, int new)
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{
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td->limit_index = new;
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td->low_downgrade_time = jiffies;
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}
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static bool throtl_tg_can_downgrade(struct throtl_grp *tg)
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{
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struct throtl_data *td = tg->td;
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unsigned long now = jiffies;
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/*
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* If cgroup is below low limit, consider downgrade and throttle other
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* cgroups
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*/
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if (time_after_eq(now, td->low_upgrade_time + throtl_slice) &&
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time_after_eq(now, tg_last_low_overflow_time(tg) + throtl_slice))
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return true;
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return false;
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}
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static bool throtl_hierarchy_can_downgrade(struct throtl_grp *tg)
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{
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while (true) {
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if (!throtl_tg_can_downgrade(tg))
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return false;
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tg = sq_to_tg(tg->service_queue.parent_sq);
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if (!tg || !tg_to_blkg(tg)->parent)
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break;
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}
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return true;
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}
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static void throtl_downgrade_check(struct throtl_grp *tg)
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{
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uint64_t bps;
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unsigned int iops;
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unsigned long elapsed_time;
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unsigned long now = jiffies;
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if (tg->td->limit_index != LIMIT_MAX ||
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!tg->td->limit_valid[LIMIT_LOW])
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return;
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if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
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return;
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if (time_after(tg->last_check_time + throtl_slice, now))
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return;
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elapsed_time = now - tg->last_check_time;
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tg->last_check_time = now;
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if (time_before(now, tg_last_low_overflow_time(tg) + throtl_slice))
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return;
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if (tg->bps[READ][LIMIT_LOW]) {
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bps = tg->last_bytes_disp[READ] * HZ;
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do_div(bps, elapsed_time);
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if (bps >= tg->bps[READ][LIMIT_LOW])
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tg->last_low_overflow_time[READ] = now;
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}
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if (tg->bps[WRITE][LIMIT_LOW]) {
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bps = tg->last_bytes_disp[WRITE] * HZ;
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do_div(bps, elapsed_time);
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if (bps >= tg->bps[WRITE][LIMIT_LOW])
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tg->last_low_overflow_time[WRITE] = now;
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}
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if (tg->iops[READ][LIMIT_LOW]) {
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iops = tg->last_io_disp[READ] * HZ / elapsed_time;
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if (iops >= tg->iops[READ][LIMIT_LOW])
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tg->last_low_overflow_time[READ] = now;
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}
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if (tg->iops[WRITE][LIMIT_LOW]) {
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iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
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if (iops >= tg->iops[WRITE][LIMIT_LOW])
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tg->last_low_overflow_time[WRITE] = now;
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}
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/*
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* If cgroup is below low limit, consider downgrade and throttle other
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* cgroups
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*/
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if (throtl_hierarchy_can_downgrade(tg))
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throtl_downgrade_state(tg->td, LIMIT_LOW);
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tg->last_bytes_disp[READ] = 0;
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tg->last_bytes_disp[WRITE] = 0;
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tg->last_io_disp[READ] = 0;
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tg->last_io_disp[WRITE] = 0;
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}
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bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
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struct bio *bio)
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{
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@ -1632,12 +1780,16 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
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again:
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while (true) {
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if (tg->last_low_overflow_time[rw] == 0)
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tg->last_low_overflow_time[rw] = jiffies;
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throtl_downgrade_check(tg);
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/* throtl is FIFO - if bios are already queued, should queue */
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if (sq->nr_queued[rw])
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break;
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/* if above limits, break to queue */
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if (!tg_may_dispatch(tg, bio, NULL)) {
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tg->last_low_overflow_time[rw] = jiffies;
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if (throtl_can_upgrade(tg->td, tg)) {
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throtl_upgrade_state(tg->td);
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goto again;
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@ -1681,6 +1833,8 @@ again:
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tg->io_disp[rw], tg_iops_limit(tg, rw),
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sq->nr_queued[READ], sq->nr_queued[WRITE]);
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tg->last_low_overflow_time[rw] = jiffies;
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bio_associate_current(bio);
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tg->td->nr_queued[rw]++;
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throtl_add_bio_tg(bio, qn, tg);
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@ -1791,6 +1945,8 @@ int blk_throtl_init(struct request_queue *q)
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td->limit_valid[LIMIT_MAX] = true;
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td->limit_index = LIMIT_MAX;
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td->low_upgrade_time = jiffies;
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td->low_downgrade_time = jiffies;
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/* activate policy */
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ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
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if (ret)
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