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    SubjectRe: workqueue thing
    On 12/21/2009 12:09, Andi Kleen wrote:
    > On Mon, Dec 21, 2009 at 10:17:54AM +0100, Jens Axboe wrote:
    >> On Fri, Dec 18 2009, Arjan van de Ven wrote:
    >>> in addition, threads are cheap. Linux has no technical problem with
    >>> running 100's of kernel threads (if not 1000s); they cost basically a
    >>> task struct and a stack (2 pages) each and that's about it. making an
    >>> elaborate-and-thus-fragile design to save a few kernel threads is
    >>> likely a bad design direction...
    >>
    >> One would hope not, since that is by no means outside of what you see on
    >> boxes today... Thousands. The fact that they are cheap, is not an
    >> argument against doing it right. Conceptually, I think the concurrency
    >> managed work queue pool is a much cleaner (and efficient) design.
    >
    > Agreed. Even if possible thousands of threads waste precious cache.

    only used ones waste cache ;-)

    > And they look ugly in ps.

    that we could solve by making them properly threads of each other; ps and co
    already (at least by default) fold threads of the same program into one.

    >
    > Also the nice thing about dynamically sizing the thread pool
    > is that if something bad (error condition that takes long) happens
    > in one work queue for a specific subsystem there's still a chance
    > to make process with other operations in the same subsystem.

    yup
    same is true for hitting some form of contention; just make an extra thread
    so that the rest can continue.


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