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

* 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

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