Re: [PATCH 2/2] perf lock: New subcommand "lock" to perf for analyzinglock statistics

[Xiao Guangrong]

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
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