Re: [PATCHSET 0/6] perf lock: Add contention subcommand (v1)

[Ingo Molnar <mingo@kernel.org>]

* Namhyung Kim <namhyung@kernel.org> wrote:

> Hello,
> 
> It's to add a new subcommand 'contention' (shortly 'con') to perf lock.
> 
> The new subcommand is to handle the new lock:contention_{begin,end}
> tracepoints and shows lock type and caller address like below:
> 
>   $ perf lock contention
>    contended   total wait     max wait     avg wait         type   caller
> 
>          238      1.41 ms     29.20 us      5.94 us     spinlock   update_blocked_averages+0x4c
>            1    902.08 us    902.08 us    902.08 us      rwsem:R   do_user_addr_fault+0x1dd
>           81    330.30 us     17.24 us      4.08 us     spinlock   _nohz_idle_balance+0x172
>            2     89.54 us     61.26 us     44.77 us     spinlock   do_anonymous_page+0x16d
>           24     78.36 us     12.27 us      3.27 us        mutex   pipe_read+0x56
>            2     71.58 us     59.56 us     35.79 us     spinlock   __handle_mm_fault+0x6aa
>            6     25.68 us      6.89 us      4.28 us     spinlock   do_idle+0x28d
>            1     18.46 us     18.46 us     18.46 us      rtmutex   exec_fw_cmd+0x21b
>            3     15.25 us      6.26 us      5.08 us     spinlock   tick_do_update_jiffies64+0x2c
>    ...

Wouldn't it also be useful to display a lock contention percentage value, 
the ratio of fastpath vs. contended/wait events?

That's usually the first-approximation metric to see how contended 
different locks are, and the average wait time quantifies it.

Thanks,

	Ingo