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Date: Fri, 06 Mar 2015 19:11:51 +0100 From: Mike Galbraith <efault@....de> To: David Ahern <david.ahern@...cle.com> Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: NMI watchdog triggering during load_balance On Fri, 2015-03-06 at 08:01 -0700, David Ahern wrote: > On 3/5/15 9:52 PM, Mike Galbraith wrote: > >> CPU970 attaching sched-domain: > >> domain 0: span 968-975 level SIBLING > >> groups: 8 single CPU groups > >> domain 1: span 968-975 level MC > >> groups: 1 group with 8 cpus > >> domain 2: span 768-1023 level CPU > >> groups: 4 groups with 256 cpus per group > > > > Wow, that topology is horrid. I'm not surprised that your box is > > writhing in agony. Can you twiddle that? > > > > twiddle that how? That was the question, _do_ you have any control, because that topology is toxic. I guess your reply means 'nope'. > The system has 4 physical cpus (sockets). Each cpu has 32 cores with 8 > threads per core and each cpu has 4 memory controllers. Thank god I've never met one of these, looks like the box from hell :) > If I disable SCHED_MC and CGROUPS_SCHED (group scheduling) there is a > noticeable improvement -- watchdog does not trigger and I do not get the > rq locks held for 2-3 seconds. But there is still fairly high cpu usage > for an idle system. Perhaps I should leave SCHED_MC on and disable > SCHED_SMT; I'll try that today. Well, if you disable SMT,your troubles _should_ shrink radically, as your box does. You should probably look at why you have CPU domains. You don't ever want to see that on a NUMA box. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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