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Date: Fri, 19 Sep 2014 13:46:22 +0100 From: Juri Lelli <juri.lelli@....com> To: Daniel Wagner <daniel.wagner@...-carit.de>, "peterz@...radead.org" <peterz@...radead.org> CC: "mingo@...hat.com" <mingo@...hat.com>, "juri.lelli@...il.com" <juri.lelli@...il.com>, "raistlin@...ux.it" <raistlin@...ux.it>, "michael@...rulasolutions.com" <michael@...rulasolutions.com>, "fchecconi@...il.com" <fchecconi@...il.com>, "vincent@...out.info" <vincent@...out.info>, "luca.abeni@...tn.it" <luca.abeni@...tn.it>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Li Zefan <lizefan@...wei.com>, "cgroups@...r.kernel.org" <cgroups@...r.kernel.org> Subject: Re: [PATCH 2/3] sched/deadline: fix bandwidth check/update when migrating tasks between exclusive cpusets Hi Daniel, On 19/09/14 12:47, Daniel Wagner wrote: > Hi, > > On 09/19/2014 11:22 AM, Juri Lelli wrote: >> Exclusive cpusets are the only way users can restrict SCHED_DEADLINE tasks >> affinity (performing what is commonly called clustered scheduling). >> Unfortunately, such thing is currently broken for two reasons: >> >> - No check is performed when the user tries to attach a task to >> an exlusive cpuset (recall that exclusive cpusets have an >> associated maximum allowed bandwidth). >> >> - Bandwidths of source and destination cpusets are not correctly >> updated after a task is migrated between them. >> >> This patch fixes both things at once, as they are opposite faces >> of the same coin. >> >> The check is performed in cpuset_can_attach(), as there aren't any >> points of failure after that function. The updated is split in two >> halves. We first reserve bandwidth in the destination cpuset, after >> we pass the check in cpuset_can_attach(). And we then release >> bandwidth from the source cpuset when the task's affinity is >> actually changed. Even if there can be time windows when sched_setattr() >> may erroneously fail in the source cpuset, we are fine with it, as >> we can't perfom an atomic update of both cpusets at once. >> >> Reported-by: Daniel Wagner <daniel.wagner@...-carit.de> > > Ack > > I have no special test for this, I just let my test running which was > fixed by patch #1. Works fine though. I'll plan to write some test for this. > Ok, thanks. Just mind that the problem fixed by patch 3/3 may sometime affect this too. I should have definitely put 3/3 on top of the patchset :/. Thanks, - Juri -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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