Messages in this thread | | | Date | Mon, 2 Sep 2013 19:26:59 +0200 | From | Andi Kleen <> | Subject | Re: perf_event: rdpmc self-monitoring overhead issue |
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> I assume he means MAP_POPULATE
Yes.
> > which does improve things, from ~3000 cycles to ~219 cycles but that's > still more overhead than the ~130 or so you get by manually touching the > page first.
That seems odd. It should be the same.
Can you do a trace-cmd function trace and compare the two cases?
trace-cmd record -p function_graph ... trace-cmd report
(as usual for tracing perf remove the useless -pg removal for perf in kernel/events/Makefile and arch/x86/kernel/cpu/Makefile first)
-Andi
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