linux-kernel - Re: [PATCH 0/2] workqueue: fix a bug when numa mapping is changed

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Date:	Thu, 26 Mar 2015 12:12:53 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Gu Zheng <guz.fnst@...fujitsu.com>, <linux-kernel@...r.kernel.org>
CC:	<tj@...nel.org>, <laijs@...fujitsu.com>,
	<isimatu.yasuaki@...fujitsu.com>, <tangchen@...fujitsu.com>,
	<izumi.taku@...fujitsu.com>
Subject: Re: [PATCH 0/2] workqueue: fix a bug when numa mapping is changed

On 2015/03/26 11:17, Gu Zheng wrote:
> Yasuaki Ishimatsu found that with node online/offline, cpu<->node
> relationship is established. Because workqueue uses a info which was
> established at boot time, but it may be changed by node hotpluging.
> 
> Once pool->node points to a stale node, following allocation failure
> happens.
>    ==
>       SLUB: Unable to allocate memory on node 2 (gfp=0x80d0)
>        cache: kmalloc-192, object size: 192, buffer size: 192, default
> order:
>      1, min order: 0
>        node 0: slabs: 6172, objs: 259224, free: 245741
>        node 1: slabs: 3261, objs: 136962, free: 127656
>    ==
> 
> As the apicid <--> node relationship is persistent, so the root cause is the
　　　　 ^^^^^^^
           pxm.

> cpu-id <-> lapicid mapping is not persistent (because the currently implementation
> always choose the first free cpu id for the new added cpu), so if we can build
> persistent cpu-id <-> lapicid relationship, this problem will be fixed.
> 
> Please refer to https://lkml.org/lkml/2015/2/27/145 for the previous discussion.
> 
> Gu Zheng (2):
>    x86/cpu hotplug: make lapicid <-> cpuid mapping persistent
>    workqueue: update per cpu workqueue's numa affinity when cpu
>      preparing online

why patch(2/2) required ?

Thanks,
-Kame

> 
>   arch/x86/kernel/apic/apic.c |   31 ++++++++++++++++++++++++++++++-
>   kernel/workqueue.c          |    1 +
>   2 files changed, 31 insertions(+), 1 deletions(-)
> 


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