Messages in this thread | | | Date | Wed, 5 Sep 2012 15:29:39 +0200 | From | Ingo Molnar <> | Subject | Re: [tip:sched/core] sched: Fix load avg vs cpu-hotplug |
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* Peter Zijlstra <peterz@infradead.org> wrote:
> 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.
Sigh.
> Ingo can you still make it go away or should I do a delta?
Please do a delta.
Thanks,
Ingo
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