From: "tip-bot2 for Valentin Schneider" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Valentin Schneider <valentin.schneider@arm.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/core] sched/fair: Clean up active balance nr_balance_failed trickery
Date: Fri, 09 Apr 2021 16:14:31 -0000 [thread overview]
Message-ID: <161798487149.29796.18250747063112261212.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210407220628.3798191-3-valentin.schneider@arm.com>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 23fb06d9602b0fcfa1a16357a5d7a7f7076a39e2
Gitweb: https://git.kernel.org/tip/23fb06d9602b0fcfa1a16357a5d7a7f7076a39e2
Author: Valentin Schneider <valentin.schneider@arm.com>
AuthorDate: Wed, 07 Apr 2021 23:06:27 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 09 Apr 2021 18:02:20 +02:00
sched/fair: Clean up active balance nr_balance_failed trickery
When triggering an active load balance, sd->nr_balance_failed is set to
such a value that any further can_migrate_task() using said sd will ignore
the output of task_hot().
This behaviour makes sense, as active load balance intentionally preempts a
rq's running task to migrate it right away, but this asynchronous write is
a bit shoddy, as the stopper thread might run active_load_balance_cpu_stop
before the sd->nr_balance_failed write either becomes visible to the
stopper's CPU or even happens on the CPU that appended the stopper work.
Add a struct lb_env flag to denote active balancing, and use it in
can_migrate_task(). Remove the sd->nr_balance_failed write that served the
same purpose. Cleanup the LBF_DST_PINNED active balance special case.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210407220628.3798191-3-valentin.schneider@arm.com
---
kernel/sched/fair.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1ad929b..356637a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7453,6 +7453,7 @@ enum migration_type {
#define LBF_NEED_BREAK 0x02
#define LBF_DST_PINNED 0x04
#define LBF_SOME_PINNED 0x08
+#define LBF_ACTIVE_LB 0x10
struct lb_env {
struct sched_domain *sd;
@@ -7614,10 +7615,13 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
* our sched_group. We may want to revisit it if we couldn't
* meet load balance goals by pulling other tasks on src_cpu.
*
- * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
- * already computed one in current iteration.
+ * Avoid computing new_dst_cpu
+ * - for NEWLY_IDLE
+ * - if we have already computed one in current iteration
+ * - if it's an active balance
*/
- if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
+ if (env->idle == CPU_NEWLY_IDLE ||
+ env->flags & (LBF_DST_PINNED | LBF_ACTIVE_LB))
return 0;
/* Prevent to re-select dst_cpu via env's CPUs: */
@@ -7642,10 +7646,14 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
/*
* Aggressive migration if:
- * 1) destination numa is preferred
- * 2) task is cache cold, or
- * 3) too many balance attempts have failed.
+ * 1) active balance
+ * 2) destination numa is preferred
+ * 3) task is cache cold, or
+ * 4) too many balance attempts have failed.
*/
+ if (env->flags & LBF_ACTIVE_LB)
+ return 1;
+
tsk_cache_hot = migrate_degrades_locality(p, env);
if (tsk_cache_hot == -1)
tsk_cache_hot = task_hot(p, env);
@@ -9836,9 +9844,6 @@ more_balance:
active_load_balance_cpu_stop, busiest,
&busiest->active_balance_work);
}
-
- /* We've kicked active balancing, force task migration. */
- sd->nr_balance_failed = sd->cache_nice_tries+1;
}
} else {
sd->nr_balance_failed = 0;
@@ -9988,13 +9993,7 @@ static int active_load_balance_cpu_stop(void *data)
.src_cpu = busiest_rq->cpu,
.src_rq = busiest_rq,
.idle = CPU_IDLE,
- /*
- * can_migrate_task() doesn't need to compute new_dst_cpu
- * for active balancing. Since we have CPU_IDLE, but no
- * @dst_grpmask we need to make that test go away with lying
- * about DST_PINNED.
- */
- .flags = LBF_DST_PINNED,
+ .flags = LBF_ACTIVE_LB,
};
schedstat_inc(sd->alb_count);
next prev parent reply other threads:[~2021-04-09 16:14 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-07 22:06 [PATCH v5 0/3] sched/fair: load-balance vs capacity margins Valentin Schneider
2021-04-07 22:06 ` [PATCH v5 1/3] sched/fair: Ignore percpu threads for imbalance pulls Valentin Schneider
2021-04-09 11:24 ` [tip: sched/core] " tip-bot2 for Lingutla Chandrasekhar
2021-04-09 12:05 ` tip-bot2 for Lingutla Chandrasekhar
2021-04-09 16:14 ` tip-bot2 for Lingutla Chandrasekhar
2021-04-14 5:21 ` [sched/fair] 38ac256d1c: stress-ng.vm-segv.ops_per_sec -13.8% regression kernel test robot
2021-04-14 17:17 ` Valentin Schneider
2021-04-21 3:20 ` Oliver Sang
2021-04-21 10:27 ` Valentin Schneider
2021-04-21 12:03 ` Peter Zijlstra
2021-04-22 7:47 ` Oliver Sang
2021-04-22 9:55 ` Valentin Schneider
2021-04-22 20:42 ` Valentin Schneider
2021-04-28 22:00 ` Valentin Schneider
2021-05-06 16:11 ` Valentin Schneider
2021-04-07 22:06 ` [PATCH v5 2/3] sched/fair: Clean up active balance nr_balance_failed trickery Valentin Schneider
2021-04-09 11:24 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2021-04-09 12:05 ` tip-bot2 for Valentin Schneider
2021-04-09 16:14 ` tip-bot2 for Valentin Schneider [this message]
2021-04-07 22:06 ` [PATCH v5 3/3] sched/fair: Introduce a CPU capacity comparison helper Valentin Schneider
2021-04-09 11:24 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2021-04-09 12:05 ` tip-bot2 for Valentin Schneider
2021-04-09 16:14 ` tip-bot2 for Valentin Schneider
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=161798487149.29796.18250747063112261212.tip-bot2@tip-bot2 \
--to=tip-bot2@linutronix.de \
--cc=dietmar.eggemann@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=valentin.schneider@arm.com \
--cc=vincent.guittot@linaro.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).