Messages in this thread | | | Subject | Re: [RFC PATCH 3/3] sched/fair: Use different cachelines for readers and writers of load_avg | From | Mike Galbraith <> | Date | Tue, 01 Dec 2015 11:44:21 +0100 |
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On Tue, 2015-12-01 at 09:49 +0100, Peter Zijlstra wrote: > On Mon, Nov 30, 2015 at 10:55:02PM -0500, Waiman Long wrote: > > On 11/30/2015 05:09 PM, Peter Zijlstra wrote: > > >On Mon, Nov 30, 2015 at 02:13:32PM -0500, Waiman Long wrote: > > >>>This begs the question tough; why are you running a global load in a > > >>>cgroup; and do we really need to update this for the root cgroup? It > > >>>seems to me we don't need calc_tg_weight() for the root cgroup, it > > >>>doesn't need to normalize its weight numbers. > > >>> > > >>>That is; isn't this simply a problem we should avoid? > > >>I didn't use any cgroup in my test setup. Autogroup was enabled, though. > > >>Booting up a 4.4-rc2 kernel caused sched_create_group() to be called 56 > > >>times. > > >Yeah, can you kill autogroup and see if that helps? If not, we probably > > >should add some code to avoid calculating things for the root group. > > > > I will try that out tomorrow. However, SCHED_AUTOGROUP was enabled in the > > distribution kernels. So we still need to look at that with autogroup > > enabled. > > Meh, or just tell the people that have stupid large machines to use > noautogroup on boot (its of questionable benefit in the first place imo, > esp. on servers).
Yup (and yup). Someone should also suggest to the systemd(isease) folks that they try actually measuring before turning everything in the world on. "Oo cgroups are cool" is NOT a good reason to turn it all on :)
-Mike
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