Re: [PATCH] workqueue: update numa affinity when node hotplug

[Kamezawa Hiroyuki]

On 2015/03/03 22:18, Tejun Heo wrote:
> Hello, Kame.
>
> On Tue, Mar 03, 2015 at 03:53:46PM +0900, Kamezawa Hiroyuki wrote:
> > relationship between proximity domain and lapic id doesn't change.
> > relationship between lapic-id and cpu-id changes.
> >
> > pxm <-> memory address  : no change
> > pxm <-> lapicid         : no change
> > pxm <-> node id         : no change
> > lapicid <-> cpu id      : change.
>
> So, we're changing the cpu ID to NUMA node mapping because current
> NUMA code is ignoring PXM for memoryless nodes?  That's it?

For memory-less node case, yes.
Another problem is that lapicid <-> cpuid relationship is not persistent.


> > > > I personally thinks proper fix is building persistent cpu-id <-> lapicid relationship as
> > > > pxm does rather than creating band-aid.
> > >
> > > Oh if this is possible, I agree that's the right direction too.
> >
> > Implementation is a bit complicated now :(.
>
> Ah well, even then, the obviously right thing to do is updating NUMA
> code to always keep track of PXM information.  We don't really want to
> pile NUMA hacks in random users of NUMA code.

We'd like to start from making apicid <-> cpuid persistent because memory-less
node case doesn't cause panic.

Gu-san, how do you think ?

Thanks,
-Kame

P.S.
Finally, I want something like udev for cpuid/numaid...


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