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@xxxxxxxxxxxx> > > 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 cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
