diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 3ab0c1c704b68f0a9d5574d2a76ea252f3cc950d..7c1fe605d0d6cb2a3de837977653c187b626c040 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -466,7 +466,7 @@ struct ioc_gq {
*/
atomic64_t vtime;
atomic64_t done_vtime;
- atomic64_t abs_vdebt;
+ u64 abs_vdebt;
u64 last_vtime;
/*
@@ -1142,7 +1142,7 @@ static void iocg_kick_waitq(struct ioc_gq *iocg, struct ioc_now *now)
struct iocg_wake_ctx ctx = { .iocg = iocg };
u64 margin_ns = (u64)(ioc->period_us *
WAITQ_TIMER_MARGIN_PCT / 100) * NSEC_PER_USEC;
- u64 abs_vdebt, vdebt, vshortage, expires, oexpires;
+ u64 vdebt, vshortage, expires, oexpires;
s64 vbudget;
u32 hw_inuse;
@@ -1152,18 +1152,15 @@ static void iocg_kick_waitq(struct ioc_gq *iocg, struct ioc_now *now)
vbudget = now->vnow - atomic64_read(&iocg->vtime);
/* pay off debt */
- abs_vdebt = atomic64_read(&iocg->abs_vdebt);
- vdebt = abs_cost_to_cost(abs_vdebt, hw_inuse);
+ vdebt = abs_cost_to_cost(iocg->abs_vdebt, hw_inuse);
if (vdebt && vbudget > 0) {
u64 delta = min_t(u64, vbudget, vdebt);
u64 abs_delta = min(cost_to_abs_cost(delta, hw_inuse),
- abs_vdebt);
+ iocg->abs_vdebt);
atomic64_add(delta, &iocg->vtime);
atomic64_add(delta, &iocg->done_vtime);
- atomic64_sub(abs_delta, &iocg->abs_vdebt);
- if (WARN_ON_ONCE(atomic64_read(&iocg->abs_vdebt) < 0))
- atomic64_set(&iocg->abs_vdebt, 0);
+ iocg->abs_vdebt -= abs_delta;
}
/*
@@ -1219,12 +1216,18 @@ static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now, u64 cost)
u64 expires, oexpires;
u32 hw_inuse;
+ lockdep_assert_held(&iocg->waitq.lock);
+
/* debt-adjust vtime */
current_hweight(iocg, NULL, &hw_inuse);
- vtime += abs_cost_to_cost(atomic64_read(&iocg->abs_vdebt), hw_inuse);
+ vtime += abs_cost_to_cost(iocg->abs_vdebt, hw_inuse);
- /* clear or maintain depending on the overage */
- if (time_before_eq64(vtime, now->vnow)) {
+ /*
+ * Clear or maintain depending on the overage. Non-zero vdebt is what
+ * guarantees that @iocg is online and future iocg_kick_delay() will
+ * clear use_delay. Don't leave it on when there's no vdebt.
+ */
+ if (!iocg->abs_vdebt || time_before_eq64(vtime, now->vnow)) {
blkcg_clear_delay(blkg);
return false;
}
@@ -1258,9 +1261,12 @@ static enum hrtimer_restart iocg_delay_timer_fn(struct hrtimer *timer)
{
struct ioc_gq *iocg = container_of(timer, struct ioc_gq, delay_timer);
struct ioc_now now;
+ unsigned long flags;
+ spin_lock_irqsave(&iocg->waitq.lock, flags);
ioc_now(iocg->ioc, &now);
iocg_kick_delay(iocg, &now, 0);
+ spin_unlock_irqrestore(&iocg->waitq.lock, flags);
return HRTIMER_NORESTART;
}
@@ -1368,14 +1374,13 @@ static void ioc_timer_fn(struct timer_list *timer)
* should have woken up in the last period and expire idle iocgs.
*/
list_for_each_entry_safe(iocg, tiocg, &ioc->active_iocgs, active_list) {
- if (!waitqueue_active(&iocg->waitq) &&
- !atomic64_read(&iocg->abs_vdebt) && !iocg_is_idle(iocg))
+ if (!waitqueue_active(&iocg->waitq) && iocg->abs_vdebt &&
+ !iocg_is_idle(iocg))
continue;
spin_lock(&iocg->waitq.lock);
- if (waitqueue_active(&iocg->waitq) ||
- atomic64_read(&iocg->abs_vdebt)) {
+ if (waitqueue_active(&iocg->waitq) || iocg->abs_vdebt) {
/* might be oversleeping vtime / hweight changes, kick */
iocg_kick_waitq(iocg, &now);
iocg_kick_delay(iocg, &now, 0);
@@ -1718,28 +1723,49 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
* tests are racy but the races aren't systemic - we only miss once
* in a while which is fine.
*/
- if (!waitqueue_active(&iocg->waitq) &&
- !atomic64_read(&iocg->abs_vdebt) &&
+ if (!waitqueue_active(&iocg->waitq) && !iocg->abs_vdebt &&
time_before_eq64(vtime + cost, now.vnow)) {
iocg_commit_bio(iocg, bio, cost);
return;
}
/*
- * We're over budget. If @bio has to be issued regardless,
- * remember the abs_cost instead of advancing vtime.
- * iocg_kick_waitq() will pay off the debt before waking more IOs.
+ * We activated above but w/o any synchronization. Deactivation is
+ * synchronized with waitq.lock and we won't get deactivated as long
+ * as we're waiting or has debt, so we're good if we're activated
+ * here. In the unlikely case that we aren't, just issue the IO.
+ */
+ spin_lock_irq(&iocg->waitq.lock);
+
+ if (unlikely(list_empty(&iocg->active_list))) {
+ spin_unlock_irq(&iocg->waitq.lock);
+ iocg_commit_bio(iocg, bio, cost);
+ return;
+ }
+
+ /*
+ * We're over budget. If @bio has to be issued regardless, remember
+ * the abs_cost instead of advancing vtime. iocg_kick_waitq() will pay
+ * off the debt before waking more IOs.
+ *
* This way, the debt is continuously paid off each period with the
- * actual budget available to the cgroup. If we just wound vtime,
- * we would incorrectly use the current hw_inuse for the entire
- * amount which, for example, can lead to the cgroup staying
- * blocked for a long time even with substantially raised hw_inuse.
+ * actual budget available to the cgroup. If we just wound vtime, we
+ * would incorrectly use the current hw_inuse for the entire amount
+ * which, for example, can lead to the cgroup staying blocked for a
+ * long time even with substantially raised hw_inuse.
+ *
+ * An iocg with vdebt should stay online so that the timer can keep
+ * deducting its vdebt and [de]activate use_delay mechanism
+ * accordingly. We don't want to race against the timer trying to
+ * clear them and leave @iocg inactive w/ dangling use_delay heavily
+ * penalizing the cgroup and its descendants.
*/
if (bio_issue_as_root_blkg(bio) || fatal_signal_pending(current)) {
- atomic64_add(abs_cost, &iocg->abs_vdebt);
+ iocg->abs_vdebt += abs_cost;
if (iocg_kick_delay(iocg, &now, cost))
blkcg_schedule_throttle(rqos->q,
(bio->bi_opf & REQ_SWAP) == REQ_SWAP);
+ spin_unlock_irq(&iocg->waitq.lock);
return;
}
@@ -1756,20 +1782,6 @@ static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
* All waiters are on iocg->waitq and the wait states are
* synchronized using waitq.lock.
*/
- spin_lock_irq(&iocg->waitq.lock);
-
- /*
- * We activated above but w/o any synchronization. Deactivation is
- * synchronized with waitq.lock and we won't get deactivated as
- * long as we're waiting, so we're good if we're activated here.
- * In the unlikely case that we are deactivated, just issue the IO.
- */
- if (unlikely(list_empty(&iocg->active_list))) {
- spin_unlock_irq(&iocg->waitq.lock);
- iocg_commit_bio(iocg, bio, cost);
- return;
- }
-
init_waitqueue_func_entry(&wait.wait, iocg_wake_fn);
wait.wait.private = current;
wait.bio = bio;
@@ -1801,6 +1813,7 @@ static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
struct ioc_now now;
u32 hw_inuse;
u64 abs_cost, cost;
+ unsigned long flags;
/* bypass if disabled or for root cgroup */
if (!ioc->enabled || !iocg->level)
@@ -1820,15 +1833,28 @@ static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
iocg->cursor = bio_end;
/*
- * Charge if there's enough vtime budget and the existing request
- * has cost assigned. Otherwise, account it as debt. See debt
- * handling in ioc_rqos_throttle() for details.
+ * Charge if there's enough vtime budget and the existing request has
+ * cost assigned.
*/
if (rq->bio && rq->bio->bi_iocost_cost &&
- time_before_eq64(atomic64_read(&iocg->vtime) + cost, now.vnow))
+ time_before_eq64(atomic64_read(&iocg->vtime) + cost, now.vnow)) {
iocg_commit_bio(iocg, bio, cost);
- else
- atomic64_add(abs_cost, &iocg->abs_vdebt);
+ return;
+ }
+
+ /*
+ * Otherwise, account it as debt if @iocg is online, which it should
+ * be for the vast majority of cases. See debt handling in
+ * ioc_rqos_throttle() for details.
+ */
+ spin_lock_irqsave(&iocg->waitq.lock, flags);
+ if (likely(!list_empty(&iocg->active_list))) {
+ iocg->abs_vdebt += abs_cost;
+ iocg_kick_delay(iocg, &now, cost);
+ } else {
+ iocg_commit_bio(iocg, bio, cost);
+ }
+ spin_unlock_irqrestore(&iocg->waitq.lock, flags);
}
static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio)
@@ -1998,7 +2024,6 @@ static void ioc_pd_init(struct blkg_policy_data *pd)
iocg->ioc = ioc;
atomic64_set(&iocg->vtime, now.vnow);
atomic64_set(&iocg->done_vtime, now.vnow);
- atomic64_set(&iocg->abs_vdebt, 0);
atomic64_set(&iocg->active_period, atomic64_read(&ioc->cur_period));
INIT_LIST_HEAD(&iocg->active_list);
iocg->hweight_active = HWEIGHT_WHOLE;
diff --git a/tools/cgroup/iocost_monitor.py b/tools/cgroup/iocost_monitor.py
index 7427a5ee761b3757feaf04ff76bf3afd7a91a90c..9d8e9613008a99c4998db7d9bfd8ac4c88cf0575 100644
--- a/tools/cgroup/iocost_monitor.py
+++ b/tools/cgroup/iocost_monitor.py
@@ -159,7 +159,12 @@ class IocgStat:
else:
self.inflight_pct = 0
- self.debt_ms = iocg.abs_vdebt.counter.value_() / VTIME_PER_USEC / 1000
+ # vdebt used to be an atomic64_t and is now u64, support both
+ try:
+ self.debt_ms = iocg.abs_vdebt.counter.value_() / VTIME_PER_USEC / 1000
+ except:
+ self.debt_ms = iocg.abs_vdebt.value_() / VTIME_PER_USEC / 1000
+
self.use_delay = blkg.use_delay.counter.value_()
self.delay_ms = blkg.delay_nsec.counter.value_() / 1_000_000