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    SubjectRe: IO queuing and complete affinity with threads (was Re: [PATCH 0/8] IO queuing and complete affinity)
    On Fri, Feb 08, 2008 at 09:24:22AM +0100, Jens Axboe wrote:
    > On Fri, Feb 08 2008, Nick Piggin wrote:
    > > On Fri, Feb 08, 2008 at 08:59:55AM +0100, Jens Axboe wrote:
    > > > On Fri, Feb 08 2008, Nick Piggin wrote:
    > > > > And if you don't?
    > > >
    > > > Well if you don't ask for anything, you wont get anything :-)
    > > > As I mentioned, the patch is a playing ground for trying various setups.
    > > > Everything defaults to 'do as usual', set options to setup certain test
    > > > scenarios.
    > >
    > > I mean if you don't know the completing CPU.
    >
    > I still don't know quite what part of that patch you are referring to
    > here. If you don't have queue_affinity set, queueing a new request with
    > the hardware is generally done on the same CPU that just completed a
    > request. That is true even without any patches.

    Generally, but I guess not always. The database workloads in question
    (which you might know very well about ;)) apparently has a lot of
    queue empty and unplug conditions. Which I guess is the reason for
    Intel's initial patch.



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