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

[Gu Zheng <guz.fnst@cn.fujitsu.com>]

Hi Kame-san,

On 03/27/2015 12:42 AM, Kamezawa Hiroyuki wrote:

> On 2015/03/27 0:18, Tejun Heo wrote:
>> Hello,
>>
>> On Thu, Mar 26, 2015 at 01:04:00PM +0800, Gu Zheng wrote:
>>> wq generates the numa affinity (pool->node) for all the possible cpu's
>>> per cpu workqueue at init stage, that means the affinity of currently un-present
>>> ones' may be incorrect, so we need to update the pool->node for the new added cpu
>>> to the correct node when preparing online, otherwise it will try to create worker
>>> on invalid node if node hotplug occurred.
>>
>> If the mapping is gonna be static once the cpus show up, any chance we
>> can initialize that for all possible cpus during boot?
>>
> 
> I think the kernel can define all possible
> 
>  cpuid <-> lapicid <-> pxm <-> nodeid
> 
> mapping at boot with using firmware table information.

Could you explain more?

> 
> One concern is current x86 logic for memory-less node v.s. memory hotplug.
> (as I explained before)
> 
> My idea is
>   step1. build all possible mapping at boot cpuid <-> apicid <-> pxm <-> node id at boot.
> 
> But this may be overwritten by x86's memory less node logic. So,
>   step2. check node is online or not before calling kmalloc. If offline, use -1.
>          rather than updating workqueue's attribute.
> 
> Thanks,
> -Kame
> 
> .
>