From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org,
dietmar.eggemann@arm.com, jhugo@codeaurora.org
Subject: Re: [PATCH] sched/fair: fix load_balance redo for null imbalance
Date: Fri, 7 Sep 2018 13:37:49 +0200 [thread overview]
Message-ID: <20180907113748.GV24106@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1536306664-29827-1-git-send-email-vincent.guittot@linaro.org>
On Fri, Sep 07, 2018 at 09:51:04AM +0200, Vincent Guittot wrote:
> It can happen that load_balance finds a busiest group and then a busiest rq
> but the calculated imbalance is in fact null.
Cute. Does that happen often?
> If the calculated imbalance is null, it's useless to try to find a busiest
> rq as no task will be migrated and we can return immediately.
>
> This situation can happen with heterogeneous system or smp system when RT
> tasks are decreasing the capacity of some CPUs.
Is it the result of one of those "force_balance" conditions in
find_busiest_group() ? Should we not fix that to then return NULL
instead?
next prev parent reply other threads:[~2018-09-07 11:37 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-07 7:51 Vincent Guittot
2018-09-07 11:37 ` Peter Zijlstra [this message]
2018-09-07 12:35 ` Vincent Guittot
2018-09-07 12:55 ` Vincent Guittot
2018-09-07 12:55 ` Peter Zijlstra
2018-09-07 12:57 ` Peter Zijlstra
2018-09-07 13:08 ` Vincent Guittot
2018-09-10 10:08 ` [tip:sched/core] sched/fair: Fix load_balance redo for !imbalance tip-bot for 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=20180907113748.GV24106@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=dietmar.eggemann@arm.com \
--cc=jhugo@codeaurora.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.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
Powered by JetHome