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Date: Tue, 1 Sep 2020 14:52:56 -0400
From: Tejun Heo <tj@...nel.org>
To: axboe@...nel.dk
Cc: linux-block@...r.kernel.org, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org, kernel-team@...com, newella@...com,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 26/27] blk-iocost: add three debug stat - cost.wait, indebt and indelay
These are really cheap to collect and can be useful in debugging iocost
behavior. Add them as debug stats for now.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
block/blk-iocost.c | 77 +++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 72 insertions(+), 5 deletions(-)
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 9366527d8c12..fc897bb142bc 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -452,6 +452,9 @@ struct iocg_pcpu_stat {
struct iocg_stat {
u64 usage_us;
+ u64 wait_us;
+ u64 indebt_us;
+ u64 indelay_us;
};
/* per device-cgroup pair */
@@ -538,6 +541,9 @@ struct ioc_gq {
struct iocg_stat last_stat;
u64 last_stat_abs_vusage;
u64 usage_delta_us;
+ u64 wait_since;
+ u64 indebt_since;
+ u64 indelay_since;
/* this iocg's depth in the hierarchy and ancestors including self */
int level;
@@ -1303,9 +1309,15 @@ static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now)
}
if (delay >= MIN_DELAY) {
+ if (!iocg->indelay_since)
+ iocg->indelay_since = now->now;
blkcg_set_delay(blkg, delay * NSEC_PER_USEC);
return true;
} else {
+ if (iocg->indelay_since) {
+ iocg->local_stat.indelay_us += now->now - iocg->indelay_since;
+ iocg->indelay_since = 0;
+ }
iocg->delay = 0;
blkcg_clear_delay(blkg);
return false;
@@ -1325,8 +1337,10 @@ static void iocg_incur_debt(struct ioc_gq *iocg, u64 abs_cost,
* Once in debt, debt handling owns inuse. @iocg stays at the minimum
* inuse donating all of it share to others until its debt is paid off.
*/
- if (!iocg->abs_vdebt && abs_cost)
+ if (!iocg->abs_vdebt && abs_cost) {
+ iocg->indebt_since = now->now;
propagate_weights(iocg, iocg->active, 0, false, now);
+ }
iocg->abs_vdebt += abs_cost;
@@ -1348,9 +1362,13 @@ static void iocg_pay_debt(struct ioc_gq *iocg, u64 abs_vpay,
iocg->abs_vdebt -= min(abs_vpay, iocg->abs_vdebt);
/* if debt is paid in full, restore inuse */
- if (!iocg->abs_vdebt)
+ if (!iocg->abs_vdebt) {
+ iocg->local_stat.indebt_us += now->now - iocg->indebt_since;
+ iocg->indebt_since = 0;
+
propagate_weights(iocg, iocg->active, iocg->last_inuse,
false, now);
+ }
}
static int iocg_wake_fn(struct wait_queue_entry *wq_entry, unsigned mode,
@@ -1436,8 +1454,17 @@ static void iocg_kick_waitq(struct ioc_gq *iocg, bool pay_debt,
__wake_up_locked_key(&iocg->waitq, TASK_NORMAL, &ctx);
- if (!waitqueue_active(&iocg->waitq))
+ if (!waitqueue_active(&iocg->waitq)) {
+ if (iocg->wait_since) {
+ iocg->local_stat.wait_us += now->now - iocg->wait_since;
+ iocg->wait_since = 0;
+ }
return;
+ }
+
+ if (!iocg->wait_since)
+ iocg->wait_since = now->now;
+
if (WARN_ON_ONCE(ctx.vbudget >= 0))
return;
@@ -1579,8 +1606,15 @@ static void iocg_flush_stat_one(struct ioc_gq *iocg, struct ioc_now *now)
iocg->usage_delta_us = div64_u64(vusage_delta, ioc->vtime_base_rate);
iocg->local_stat.usage_us += iocg->usage_delta_us;
+ /* propagate upwards */
new_stat.usage_us =
iocg->local_stat.usage_us + iocg->desc_stat.usage_us;
+ new_stat.wait_us =
+ iocg->local_stat.wait_us + iocg->desc_stat.wait_us;
+ new_stat.indebt_us =
+ iocg->local_stat.indebt_us + iocg->desc_stat.indebt_us;
+ new_stat.indelay_us =
+ iocg->local_stat.indelay_us + iocg->desc_stat.indelay_us;
/* propagate the deltas to the parent */
if (iocg->level > 0) {
@@ -1589,6 +1623,12 @@ static void iocg_flush_stat_one(struct ioc_gq *iocg, struct ioc_now *now)
parent_stat->usage_us +=
new_stat.usage_us - iocg->last_stat.usage_us;
+ parent_stat->wait_us +=
+ new_stat.wait_us - iocg->last_stat.wait_us;
+ parent_stat->indebt_us +=
+ new_stat.indebt_us - iocg->last_stat.indebt_us;
+ parent_stat->indelay_us +=
+ new_stat.indelay_us - iocg->last_stat.indelay_us;
}
iocg->last_stat = new_stat;
@@ -1961,8 +2001,6 @@ static void ioc_timer_fn(struct timer_list *timer)
return;
}
- iocg_flush_stat(&ioc->active_iocgs, &now);
-
/*
* Waiters determine the sleep durations based on the vrate they
* saw at the time of sleep. If vrate has increased, some waiters
@@ -1976,6 +2014,22 @@ static void ioc_timer_fn(struct timer_list *timer)
spin_lock(&iocg->waitq.lock);
+ /* flush wait and indebt stat deltas */
+ if (iocg->wait_since) {
+ iocg->local_stat.wait_us += now.now - iocg->wait_since;
+ iocg->wait_since = now.now;
+ }
+ if (iocg->indebt_since) {
+ iocg->local_stat.indebt_us +=
+ now.now - iocg->indebt_since;
+ iocg->indebt_since = now.now;
+ }
+ if (iocg->indelay_since) {
+ iocg->local_stat.indelay_us +=
+ now.now - iocg->indelay_since;
+ iocg->indelay_since = now.now;
+ }
+
if (waitqueue_active(&iocg->waitq) || iocg->abs_vdebt ||
iocg->delay) {
/* might be oversleeping vtime / hweight changes, kick */
@@ -2010,6 +2064,12 @@ static void ioc_timer_fn(struct timer_list *timer)
}
commit_weights(ioc);
+ /*
+ * Wait and indebt stat are flushed above and the donation calculation
+ * below needs updated usage stat. Let's bring stat up-to-date.
+ */
+ iocg_flush_stat(&ioc->active_iocgs, &now);
+
/* calc usage and see whether some weights need to be moved around */
list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
u64 vdone, vtime, usage_us, usage_dur;
@@ -2835,6 +2895,13 @@ static size_t ioc_pd_stat(struct blkg_policy_data *pd, char *buf, size_t size)
pos += scnprintf(buf + pos, size - pos, " cost.usage=%llu",
iocg->last_stat.usage_us);
+ if (blkcg_debug_stats)
+ pos += scnprintf(buf + pos, size - pos,
+ " cost.wait=%llu cost.indebt=%llu cost.indelay=%llu",
+ iocg->last_stat.wait_us,
+ iocg->last_stat.indebt_us,
+ iocg->last_stat.indelay_us);
+
return pos;
}
--
2.26.2
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