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SubjectRe: [PATCH 34/35] async: use workqueue for worker pool
On 6/29/2010 10:12 AM, Tejun Heo wrote:
> On 06/29/2010 06:59 PM, Tejun Heo wrote:
>
>> Hello, Arjan.
>>
>> On 06/29/2010 06:40 PM, Arjan van de Ven wrote:
>>
>>> uh? clearly the assumption is that if I have a 16 CPU machine, and 12
>>> items of work get scheduled,
>>> that we get all 12 running in parallel. All the smarts of cmwq surely
>>> only kick in once you've reached the
>>> "one work item per cpu" threshold ???
>>>
>> Hmmm... workqueue workers are bound to certain cpu, so if you schedule
>> a work on a specific CPU, it will run there. Once a cpu gets
>> saturated, the issuing thread will be moved elsewhere. I don't think
>> it matters to any of the current async users one way or the other,
>> would it?
>>
> Thinking more about it. It's now not difficult to add a gcwq for an
> unbound pseudo CPU number and use it as host for workers which can run
> on any CPU. The automatic concurrency management doesn't make much
> sense for those workers, so @max_active can be used as the explicit
> concurrency throttle. It's not even gonna take a lot of code but I'm
> just not convinced that there's much benefit in doing that. So, yeah,
> if necessary, sure, but let's think whether it's gonna be actually
> useful.
>


the point in general is to get maximum parallelism; with systems getting
more and more cores, maximum parallelism is
a good design goal.



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