Messages in this thread | | | Date | Thu, 20 Aug 2009 12:04:03 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] better align percpu counter (Was Re: [tip:sched/core] sched: cpuacct: Use bigger percpu counter batch values for stats counters |
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* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Thu, 20 Aug 2009 16:24:51 +1000 > Anton Blanchard <anton@samba.org> wrote: > > > > > Hi, > > > > > Could you share contex-switch-test program ? > > > I'd like to play with it to find out what I can do against percpu counter. > > > > Sure: > > > > http://ozlabs.org/~anton/junkcode/context_switch.c > > > > Very simple, just run it once per core: > > > > for i in `seq 0 31` > > do > > taskset -c $i ./context_switch & > > done > > > > Then look at the context switch rates in vmstat. > > > Thank you for test program. > > Before adjusting batch counter (I think you should modify it), > Could you try this ? > > I only have 8cpu(2socket) host but works well. > (But...my host is x86-64 and has not virt-cpu-accouting.) > > with your program > before patch. > cpuacct off : 414000-416000 ctsw per sec. > cpuacct on : 401000-404000 ctsw per sec. > > after patch > cpuacct on : 412000-413000 ctsw per sec. > > Maybe I should check cache-miss late ;)
Btw., in latest upstream you can do that via:
cd tools/perf/ make -j install
perf stat --repeat 5 -- taskset -c 1 ./context_switch
there will be cache-miss and other stats, error bars so you can compare the before/after better, etc.
Ingo
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