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SubjectRe: [PATCH 2/2] perf lock: New subcommand "lock" to perf for analyzing lock statistics
On Mon, Dec 07, 2009 at 08:48:05PM +0100, Frederic Weisbecker wrote:
> On Mon, Dec 07, 2009 at 04:38:03PM +0800, Xiao Guangrong wrote:
> >
> >
> > Ingo Molnar wrote:
> >
> > > Also, i agree that the performance aspect is probably the most pressing
> > > issue. Note that 'perf bench sched messaging' is very locking intense so
> > > a 10x slowdown is not entirely unexpected - we still ought to optimize
> > > it all some more. 'perf lock' is an excellent testcase for this in any
> > > case.
> > >
> >
> > Here are some test results to show the overhead of lockdep trace events:
> >
> > select pagefault mmap Memory par Cont_SW
> > latency latency latency R/W BD latency
> >
> > disable ftrace 0 0 0 0 0
> >
> > enable all ftrace -16.65% -109.80% -93.62% 0.14% -6.94%
> >
> > enable all ftrace -2.67% 1.08% -3.65% -0.52% -0.68%
> > except lockdep
> >
> >
> > We also found big overhead when using kernbench and fio, but we haven't
> > verified whether it's caused by lockdep events.
> >
> > Thanks,
> > Xiao
>
>
> This profile has been done using ftrace with perf right?
> It might be because the lock events are high rate events and
> fill a lot of perf buffer space. More than other events.
> In one of your previous mails, you showed us the difference
> of the size of perf.data by capturing either scheduler events
> or lock events.



I'm not sure who sent this email actually. May be you or Hitoshi.

But, anyway you got the point :)



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