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    SubjectRe: CFQ IO scheduler patch series - AIM7 DBase results on a 16-way IA64
    Jens Axboe wrote:
    > On Mon, May 21 2007, Alan D. Brunelle wrote:
    >
    >> Jens Axboe wrote:
    >>
    >>> On Tue, May 01 2007, Alan D. Brunelle wrote:
    >>>
    >>>
    >>>> Jens Axboe wrote:
    >>>>
    >>>>
    >>>>> On Mon, Apr 30 2007, Alan D. Brunelle wrote:
    >>>>>
    >>>>>
    >>>>>> The results from a single run of an AIM7 DBase load on a 16-way ia64
    >>>>>> box (64GB RAM + 144 FC disks) showed a slight regression (~0.5%) by
    >>>>>> adding in this patch. (Graph can be found at
    >>>>>> http://free.linux.hp.com/~adb/cfq/cfq_dbase.png ) It is only a single
    >>>>>> set of runs, on a single platform, but it is something to keep an eye
    >>>>>> on as the regression showed itself across the complete run.
    >>>>>>
    >>>>>>
    >>>>> Do you know if this regression is due to worse IO performance, or
    >>>>> increased system CPU usage?
    >>>>>
    >>>>>
    >>>> We performed two point runs yesterday (20,000 and 50,000 tasks) and here
    >>>> are the results:
    >>>>
    >>>> Kernel Tasks Jobs per Minute %sys (avg)
    >>>> ------ ----- --------------- ----------
    >>>> 2.6.21 20000 60,831.1 39.83%
    >>>> CFQ br 20000 60,237.4 40.80%
    >>>> -0.98% +2.44%
    >>>>
    >>>> 2.6.21 50000 60,881.6 40.43%
    >>>> CFQ br 50000 60,400.6 40.80%
    >>>> -0.79% +0.92%
    >>>>
    >>>> So we're seeing a slight IO performance regression with a slight
    >>>> increase in %system with the CFQ branch. (A chart of the complete run
    >>>> values is up on http://free.linux.hp.com/~adb/cfq/cfq_20k50k.png ).
    >>>>
    >>>>
    >>> Alan, can you repeat that same run with this patch applied? It
    >>> reinstates the cfq lookup hash, which could account for increased system
    >>> utilization.
    >>>
    >>>
    >> Hi Jens -
    >>
    >> This test was performed over the weekend, results are updated on
    >>
    >> http://free.linux.hp.com/~adb/cfq/cfq_dbase.png
    >>
    >
    > Thanks a lot, Alan! So the cfq hash does indeed improve things a little,
    > that's a shame. I guess I'll just reinstate the hash lookup.
    >
    >
    You're welcome Jens, but remember: It's one set of data; from one
    benchmark; on one architecture; on one platform...don't know if you
    should scrap the whole thing for that! :-) At the very least, I could
    look into trying it out on another architecture. Let me see what I can
    dig up...

    Alan
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