Messages in this thread | | | Subject | tbench regression with 2.6.32-rc1 | From | "Zhang, Yanmin" <> | Date | Fri, 09 Oct 2009 17:51:29 +0800 |
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Comparing with 2.6.31's results, tebench has some regression with 2.6.32-rc1. COmmandline to start tbench: #./tbench_srv & #./tbench -t 600 CPU_NUM*2 127.0.0.1 #Use real cpu num to replace CPU_NUM So start 2 client processes per cpu.
1) On 4*4 core tigerton: 30%; 2) On 2*4 core stoakley: 15%; 3) On 2*8 core Nehalem: 6%.
As there are couple of patches which try to turn on/off some sched domain flags such like SD_BALANCE_WAKE, I used some walkaround to bisect it. On tigerton, below patch is captured. commit 59abf02644c45f1591e1374ee7bb45dc757fcb88 Author: Peter Zijlstra <a.p.zijlstra@chello.nl> Date: Wed Sep 16 08:28:30 2009 +0200
sched: Add SD_PREFER_LOCAL
The patch reverting is not clean, so I did some testing by turning on/off some domain flags and sched_feaures manually.
1) On tigerton: if SD_PREFER_LOCAL=0 (disable it), the regression becomes about 2%. 2) On stoakley: if SD_PREFER_LOCAL=0 (disable it), the regression becomes about 4%. 3) On Nehalem: Above method couldn't improve result. I'm still checking it.
I also tried to turn on/off FAIR_SLEEPERS and GENTLE_FAIR_SLEEPERS. It seems they has limited impact on tbench. I need double check these 2 flags.
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