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

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Date:	Wed, 4 Mar 2015 14:45:47 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Gu Zheng <guz.fnst@...fujitsu.com>, <linux-kernel@...r.kernel.org>,
	<laijs@...fujitsu.com>, <isimatu.yasuaki@...fujitsu.com>,
	<tangchen@...fujitsu.com>
Subject: Re: [PATCH] workqueue: update numa affinity when node hotplug

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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