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
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