lkml.org 
[lkml]   [2015]   [Apr]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Topology updates and NUMA-level sched domains
On 08.04.2015 [12:52:12 +0200], Peter Zijlstra wrote:
> On Wed, Apr 08, 2015 at 12:32:01PM +0200, Brice Goglin wrote:
> > Le 07/04/2015 21:41, Peter Zijlstra a écrit :
> > > No, that's very much not the same. Even if it were dealing with hotplug
> > > it would still assume the cpu to return to the same node.
> > >
> > > But mostly people do not even bother to handle hotplug.
> > >
> >
> > You said userspace assumes the cpu<->node relation is a boot-time fixed
> > one, and hotplug breaks this.
>
> I said no such thing. Regular hotplug actually respects that relation.

Wel, sort of. If you *just* hotplug a CPU out, your invariant of what
CPUs are currently available on what nodes is no longer held. Similarly
if you just add a CPU. And means that you could end up using cpumasks
that are incorrect if you don't make them at runtime, it seems?

> > How do you expect userspace to handle hotplug?
>
> Mostly not. Why would they? CPU hotplug is rare and mostly a case of:
> don't do that then.
>
> Its just that some of the virt wankers are using it for resource
> management which is entirely misguided. Then again, most of virt is.

I guess that is a matter of opinion.

-Nish



\
 
 \ /
  Last update: 2015-04-10 01:21    [W:0.077 / U:1.460 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site