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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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