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SubjectRe: [PATCH 2/2] perf lock: New subcommand "lock" to perf for analyzing lock statistics

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.


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