Re: CFQ IO scheduler patch series - AIM7 DBase results on a 16-way IA64

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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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