From: Peter Zijlstra <peterz@infradead.org>
To: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>
Subject: Re: [PATCH] sched: Relax a restriction in sched_rt_can_attach()
Date: Wed, 6 May 2015 10:49:06 +0200 [thread overview]
Message-ID: <20150506084906.GW23123@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150505190603.GZ1971@htj.duckdns.org>
On Tue, May 05, 2015 at 03:06:03PM -0400, Tejun Heo wrote:
> Hello, Peter.
>
> On Tue, May 05, 2015 at 09:00:57PM +0200, Peter Zijlstra wrote:
> > On Tue, May 05, 2015 at 12:31:12PM -0400, Tejun Heo wrote:
> > > What I don't want to happen is controllers failing migrations
> > > willy-nilly for random reasons leaving users baffled, which we've
> > > actually been doing unfortunately. Maybe we need to deal with this
> > > fixed resource arbitration as a separate class and allow them to fail
> > > migration w/ -EBUSY.
> >
> > Ah, _that_ was the problem.
> >
> > Which is something created by this co-mounting of controllers.
>
> Yeah, partly, but also that it's an extra failure mode which isn't
> necessary for most controllers.
I can agree with reducing failure modes, but we should not do it at the
cost of functionality.
> > You could of course store the ss-id of the failing operation in
> > task_struct and have a file reporting the name of the ss-id.
> >
> > That way, there is a simple way to find out which controller failed the
> > migrate.
>
> Given that the resources which can fail are very limited, I don't
> think we need that right now as long as we limit and document the
> possible failure cases clearly. Hopefully, this won't devolve into
> collection of arbitrary failures.
Right, but something like that would be fairly trivial to implement and
would give immediate resolution.
For example:
$ echo 123 > /cgroups/monkey/business/tasks
-EBUSY
$ cat /cgroups/monkey/business/errno
cpu:-EBUSY
(in fact, for a trivial implementation it doesn't matter which
cgroup/errno you cat)
next prev parent reply other threads:[~2015-05-06 8:50 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-04 0:54 [PATCH] sched: Relax a restriction in sched_rt_can_attach() Zefan Li
2015-05-04 3:13 ` Mike Galbraith
2015-05-04 4:39 ` Zefan Li
2015-05-04 5:10 ` Mike Galbraith
2015-05-04 5:39 ` Mike Galbraith
2015-05-04 9:11 ` Zefan Li
2015-05-04 12:08 ` Mike Galbraith
2015-05-04 12:37 ` Peter Zijlstra
2015-05-04 14:09 ` Mike Galbraith
2015-05-05 3:46 ` Zefan Li
2015-05-05 6:02 ` Mike Galbraith
2015-05-05 3:54 ` Zefan Li
2015-05-05 14:10 ` Peter Zijlstra
2015-05-05 14:18 ` Tejun Heo
2015-05-05 15:19 ` Peter Zijlstra
2015-05-05 16:31 ` Tejun Heo
2015-05-05 19:00 ` Peter Zijlstra
2015-05-05 19:06 ` Tejun Heo
2015-05-06 8:49 ` Peter Zijlstra [this message]
2015-05-05 14:41 ` Tejun Heo
2015-05-05 15:11 ` Peter Zijlstra
2015-05-05 16:13 ` Tejun Heo
2015-05-05 16:50 ` Peter Zijlstra
2015-05-05 18:29 ` Thomas Gleixner
2015-05-05 19:00 ` Tejun Heo
2015-05-06 9:12 ` Thomas Gleixner
2015-05-05 18:31 ` Tejun Heo
2015-05-05 14:09 ` Tejun Heo
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