Re: [PATCH 4/5] workqueue: update NUMA affinity for the node lost CPU

[Lai Jiangshan <laijs@cn.fujitsu.com>]

On 12/13/2014 01:27 AM, Tejun Heo wrote:
> On Fri, Dec 12, 2014 at 06:19:54PM +0800, Lai Jiangshan wrote:
>> We fixed the major cases when the numa mapping is changed.
>>
>> We still have the assumption that when the node<->cpu mapping is changed
>> the original node is offline, and the current code of memory-hutplug also
>> prove this.
>>
>> This assumption might be changed in future and the orig_node is still online
>> in some cases.  And in these cases, the cpumask of the pwqs of the orig_node
>> still contains the onlining CPU which is a CPU of another node, and the worker
>> may run on the onlining CPU (aka run on the wrong node).
>>
>> So we drop this assumption and make the code calls wq_update_unbound_numa()
>> to update the affinity in this case.
> 
> This is seriously obfuscating.  I really don't think meddling with
> existing pools is a good idea.  

> The foundation those pools were standing are gone.

This statement is not true unless we write some code to force them,
dequeue them from the unbound_pool_hash, for example.

> Drain and discard the pools.  Please don't try to
> retro-fit it to new foundations.
> 
> Thanks.
>