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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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