From: Peter Zijlstra <peterz@infradead.org>
To: paulmck@linux.vnet.ibm.com, mingo@kernel.org, hpa@zytor.com,
linux-kernel@vger.kernel.org, rakib.mullick@gmail.com,
tglx@linutronix.de
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:sched/core] sched: Fix load avg vs cpu-hotplug
Date: Wed, 05 Sep 2012 14:36:56 +0200 [thread overview]
Message-ID: <1346848616.2600.26.camel@twins> (raw)
In-Reply-To: <tip-f319da0c6894fcf55e21320e40506418a2aad629@git.kernel.org>
On Tue, 2012-09-04 at 11:43 -0700, tip-bot for Peter Zijlstra wrote:
> Commit-ID: f319da0c6894fcf55e21320e40506418a2aad629
> Gitweb: http://git.kernel.org/tip/f319da0c6894fcf55e21320e40506418a2aad629
> Author: Peter Zijlstra <peterz@infradead.org>
> AuthorDate: Mon, 20 Aug 2012 11:26:57 +0200
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitDate: Tue, 4 Sep 2012 14:30:18 +0200
>
> sched: Fix load avg vs cpu-hotplug
>
> Rabik and Paul reported two different issues related to the same few
> lines of code.
>
> Rabik's issue is that the nr_uninterruptible migration code is wrong in
> that he sees artifacts due to this (Rabik please do expand in more
> detail).
>
> Paul's issue is that this code as it stands relies on us using
> stop_machine() for unplug, we all would like to remove this assumption
> so that eventually we can remove this stop_machine() usage altogether.
>
> The only reason we'd have to migrate nr_uninterruptible is so that we
> could use for_each_online_cpu() loops in favour of
> for_each_possible_cpu() loops, however since nr_uninterruptible() is the
> only such loop and its using possible lets not bother at all.
>
> The problem Rabik sees is (probably) caused by the fact that by
> migrating nr_uninterruptible we screw rq->calc_load_active for both rqs
> involved.
>
> So don't bother with fancy migration schemes (meaning we now have to
> keep using for_each_possible_cpu()) and instead fold any nr_active delta
> after we migrate all tasks away to make sure we don't have any skewed
> nr_active accounting.
Oh argh.. this patch isn't actually right.. I actually removed it from
my series but forgot to update the tarball.
Ingo can you still make it go away or should I do a delta?
next prev parent reply other threads:[~2012-09-05 12:37 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-16 13:45 Add rq->nr_uninterruptible count to dest cpu's rq while CPU goes down Rakib Mullick
2012-08-16 13:56 ` Peter Zijlstra
2012-08-16 14:28 ` Rakib Mullick
2012-08-16 14:42 ` Peter Zijlstra
2012-08-16 15:32 ` Rakib Mullick
2012-08-16 17:46 ` Peter Zijlstra
2012-08-17 13:39 ` Rakib Mullick
2012-08-20 9:26 ` Peter Zijlstra
2012-08-20 16:10 ` Rakib Mullick
2012-08-20 16:16 ` Peter Zijlstra
2012-08-20 16:26 ` Paul E. McKenney
2012-08-27 18:44 ` Paul E. McKenney
2012-08-28 6:57 ` Rakib Mullick
2012-08-28 13:42 ` Paul E. McKenney
2012-08-28 16:52 ` Rakib Mullick
2012-08-28 17:07 ` Paul E. McKenney
2012-08-29 1:05 ` Rakib Mullick
2012-09-04 18:43 ` [tip:sched/core] sched: Fix load avg vs cpu-hotplug tip-bot for Peter Zijlstra
2012-09-05 12:36 ` Peter Zijlstra [this message]
2012-09-05 13:29 ` Ingo Molnar
2012-09-05 17:01 ` Peter Zijlstra
2012-09-05 17:34 ` Ingo Molnar
2012-09-05 22:03 ` Peter Zijlstra
2012-09-05 23:39 ` Paul E. McKenney
2012-09-06 3:30 ` Rakib Mullick
2012-09-14 6:14 ` [tip:sched/core] sched: Fix load avg vs. cpu-hotplug tip-bot for Peter Zijlstra
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=1346848616.2600.26.camel@twins \
--to=peterz@infradead.org \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=rakib.mullick@gmail.com \
--cc=tglx@linutronix.de \
/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).