From: Juri Lelli <juri.lelli@arm.com>
To: Daniel Wagner <daniel.wagner@bmw-carit.de>,
"peterz@infradead.org" <peterz@infradead.org>
Cc: "mingo@redhat.com" <mingo@redhat.com>,
"juri.lelli@gmail.com" <juri.lelli@gmail.com>,
"raistlin@linux.it" <raistlin@linux.it>,
"michael@amarulasolutions.com" <michael@amarulasolutions.com>,
"fchecconi@gmail.com" <fchecconi@gmail.com>,
"vincent@legout.info" <vincent@legout.info>,
"luca.abeni@unitn.it" <luca.abeni@unitn.it>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Li Zefan <lizefan@huawei.com>,
"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>
Subject: Re: [PATCH 2/3] sched/deadline: fix bandwidth check/update when migrating tasks between exclusive cpusets
Date: Fri, 19 Sep 2014 13:46:22 +0100 [thread overview]
Message-ID: <541C259E.4010207@arm.com> (raw)
In-Reply-To: <541C17D6.5020608@bmw-carit.de>
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@bmw-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
next prev parent reply other threads:[~2014-09-19 12:45 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-19 9:22 [PATCH 0/3] SCHED_DEADLINE fix AC and SMP scheduling Juri Lelli
2014-09-19 9:22 ` [PATCH 1/3] sched/deadline: clear dl_entity params when setscheduling to different class Juri Lelli
2014-09-19 11:44 ` Daniel Wagner
2014-09-19 12:43 ` Juri Lelli
2014-09-22 18:50 ` Vincent Legout
2014-09-24 14:54 ` [tip:sched/core] sched/deadline: Clear " tip-bot for Juri Lelli
2014-10-08 12:32 ` [PATCH 1/3] sched/deadline: clear " Wanpeng Li
2014-10-21 12:15 ` Wanpeng Li
2014-10-21 13:15 ` Juri Lelli
2014-09-19 9:22 ` [PATCH 2/3] sched/deadline: fix bandwidth check/update when migrating tasks between exclusive cpusets Juri Lelli
2014-09-19 11:47 ` Daniel Wagner
2014-09-19 12:46 ` Juri Lelli [this message]
2014-09-19 21:25 ` Peter Zijlstra
2014-09-23 8:12 ` Juri Lelli
2014-10-07 8:59 ` Juri Lelli
2014-10-07 12:31 ` Peter Zijlstra
2014-10-07 13:12 ` Juri Lelli
2014-10-28 11:07 ` [tip:sched/core] sched/deadline: Ensure that updates to exclusive cpusets don't break AC tip-bot for Juri Lelli
2014-09-22 19:24 ` [PATCH 2/3] sched/deadline: fix bandwidth check/update when migrating tasks between exclusive cpusets Vincent Legout
2014-09-23 8:09 ` Juri Lelli
2014-09-23 13:08 ` Daniel Wagner
2014-10-28 11:07 ` [tip:sched/core] sched/deadline: Fix bandwidth check/ update " tip-bot for Juri Lelli
2014-09-19 9:22 ` [PATCH 3/3] sched/deadline: fix inter- exclusive cpusets migrations Juri Lelli
2014-09-24 14:55 ` [tip:sched/core] sched/deadline: Fix " tip-bot for Juri Lelli
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