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)
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Cc: Zefan Li <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>, Mike Galbraith <umgwanakikbuti-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.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-piEFEHQLUPpN0TnZuCh8vA@public.gmane.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: 43+ 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 0:54 ` Zefan Li 2015-05-04 3:13 ` Mike Galbraith 2015-05-04 3:13 ` Mike Galbraith 2015-05-04 4:39 ` Zefan Li 2015-05-04 4:39 ` Zefan Li 2015-05-04 5:10 ` Mike Galbraith 2015-05-04 5:10 ` Mike Galbraith 2015-05-04 5:39 ` Mike Galbraith 2015-05-04 5:39 ` Mike Galbraith 2015-05-04 9:11 ` Zefan Li 2015-05-04 9:11 ` Zefan Li 2015-05-04 12:08 ` Mike Galbraith 2015-05-04 12:08 ` Mike Galbraith 2015-05-04 12:37 ` Peter Zijlstra 2015-05-04 12:37 ` Peter Zijlstra 2015-05-04 14:09 ` Mike Galbraith 2015-05-05 3:46 ` Zefan Li 2015-05-05 3:46 ` Zefan Li 2015-05-05 6:02 ` Mike Galbraith 2015-05-05 6:02 ` Mike Galbraith 2015-05-05 3:54 ` Zefan Li 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 2015-05-05 19:06 ` Tejun Heo 2015-05-06 8:49 ` Peter Zijlstra [this message] 2015-05-06 8:49 ` Peter Zijlstra 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 2015-05-05 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 2015-05-05 14:09 ` Tejun Heo
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