Messages in this thread | | | Date | Tue, 09 Sep 2008 12:54:15 -0400 | From | "Alan D. Brunelle" <> | Subject | Re: Benchmarking results: DSS elapsed time values w/ rq_affinity=0/1 - Jens' for-2.6.28 tree |
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Jens Axboe wrote: > Thanks a lot for these numbers Alan, it definitely looks like a clear > win (and a pretty big one) for all of the above and the previous mail. > It would be interesting to see sys and usr times seperately, as well as > trying to compare profiles of two runs. On the testing that I did with a > 4-way ppc box, lock contention and bouncing was way down with XFS and > btrfs. I didn't test other file systems yet. I saw mean acquisition and > hold time reductions in the 20-30% range and waittime reductions of over > 40% in just simple meta data intensive fs testing.
Unfortunately, ia64 does /not/ currently support the standard lockstat reporting interface. However, I was able to utilize Caliper (an HP ia64 profiler similar to Oprofile) and gathered a couple of interesting values. These are averaged over 10 runs each (10 w/ rq_affinity=0 and 10 w/ rq_affinity=1, alternating between the two).
First: For the overall system we can gauge how efficient the instruction stream is by looking at un-stalled instructions: w/ rq_affinity set to 0 we see 24.001% of the instructions were un-stalled, whilst w/ rq_affinity set to 1 we see 24.469% un-stalled (1.95% better w/ rq_affinity set to 1).
Just looking at the gross amount of cycles attributed to the application (Oracle) we see that with rq_affinity set to 0 about 70.123% of the cycles are attributed to that, whilst with rq_affinity set to 1 we see 71.520% of the cycles used by Oracle (1.99% better w/ rq_affinity set to 1).
Overall stats for the two results posted above:
Unstalled values: rq=0: min=22.180 avg=24.001 max=27.220 sdev=1.881 range=5.040 rq=1: min=23.580 avg=24.469 max=24.930 sdev=0.486 range=1.350
%Cycles attributed to Oracle: rq=0: min=69.890 avg=70.231 max=71.170 sdev=0.379 range=1.280 rq=1: min=71.420 avg=71.520 max=71.670 sdev=0.080 range=0.250
Again, in both sets we see a /much/ smaller deviation from the average amongst all the run results when rq_affinity is set to 1.
I'm going to see if an older lock stat mechanism still works w/ 2.6.27-rc5-ish kernels on ia64, and try that.
Alan
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