From: Valentin Schneider <valentin.schneider@arm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@redhat.com, peterz@infradead.org,
vincent.guittot@linaro.org, Dietmar.Eggemann@arm.com
Subject: [PATCH] sched/fair: Don't increase sd->balance_interval on newidle balance
Date: Tue, 25 Sep 2018 18:35:22 +0100 [thread overview]
Message-ID: <1537896922-8508-1-git-send-email-valentin.schneider@arm.com> (raw)
When load_balance() fails to move some load because of task affinity,
we end up increasing sd->balance_interval to delay the next periodic
balance in the hopes that next time we look, that annoying pinned
task(s) will be gone.
However, idle_balance() pays no attention to sd->balance_interval, yet
it will still lead to an increase in balance_interval in case of
pinned tasks.
If we're going through several newidle balances (e.g. we have a
periodic task), this can lead to a huge increase of the
balance_interval in a very small amount of time.
To prevent that, don't increase the balance interval when going
through a newidle balance.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
kernel/sched/fair.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6bd142d..620910d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8782,13 +8782,22 @@ static int load_balance(int this_cpu, struct rq *this_rq,
sd->nr_balance_failed = 0;
out_one_pinned:
+ ld_moved = 0;
+
+ /*
+ * idle_balance() disregards balance intervals, so we could repeatedly
+ * reach this code, which would lead to balance_interval skyrocketting
+ * in a short amount of time. Skip the balance_interval increase logic
+ * to avoid that.
+ */
+ if (env.idle == CPU_NEWLY_IDLE)
+ goto out;
+
/* tune up the balancing interval */
- if (((env.flags & LBF_ALL_PINNED) &&
- sd->balance_interval < MAX_PINNED_INTERVAL) ||
- (sd->balance_interval < sd->max_interval))
+ if ((env.flags & LBF_ALL_PINNED &&
+ sd->balance_interval < MAX_PINNED_INTERVAL) ||
+ (sd->balance_interval < sd->max_interval))
sd->balance_interval *= 2;
-
- ld_moved = 0;
out:
return ld_moved;
}
--
2.7.4
next reply other threads:[~2018-09-25 17:38 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-25 17:35 Valentin Schneider [this message]
2018-09-26 8:13 ` [PATCH] sched/fair: Don't increase sd->balance_interval on newidle balance Vincent Guittot
2018-09-26 9:35 ` Valentin Schneider
2018-09-26 10:33 ` Vincent Guittot
2018-09-26 13:16 ` Valentin Schneider
2018-09-26 13:56 ` Vincent Guittot
2018-09-26 13:17 ` Peter Zijlstra
2018-09-26 13:58 ` Vincent Guittot
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=1537896922-8508-1-git-send-email-valentin.schneider@arm.com \
--to=valentin.schneider@arm.com \
--cc=Dietmar.Eggemann@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=vincent.guittot@linaro.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).