Messages in this thread | | | Subject | Re: tbench regression with 2.6.33-rc1 | From | Peter Zijlstra <> | Date | Mon, 11 Jan 2010 13:08:00 +0100 |
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On Fri, 2009-12-25 at 19:11 +0800, Lin Ming wrote: > Hi, > > Test machine: 16 cpus (4P/2Core/HT), 8G mem > tbench test command: > tbench_srv & > tbench 32 > > Compared with 2.6.32, tbench has ~4% regression in 2.6.33-rc1. > > >From vmstat data, the context switch number also drop ~4%. > perf top data does not show much differences. > > But lockstat data shows huge difference in rq->lock, as below. > See the attachment for the full lockstat data. > > Any clue of this regression?
Nope, I thought to see the same on a dual-socket machine, but when bisecting I ended up on a user-space perf commit, which is pretty much impossible.
I did notice some variance in the numbers between boots, maybe it was large enough to fool me.. (~2800 MB/s was the good one, ~2200 MB/s was the bad one).
perf itself also didn't really provide clue, perf record -ag on the workload didn't really show anything scheduler related. vmstat 1 did show a proportional drop in context switch rate between the kernels though.. most odd.
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