* Peter Zijlstra <[email protected]> wrote:
> Use the lockdep infrastructure to track lock contention and other lock
> statistics.
>
> It tracks lock contention events, and the first four unique call-sites
> that encountered contention.
>
> It also measures lock wait-time and hold-time in nanoseconds. The
> minimum and maximum times are tracked, as well as a total (which
> together with the number of event can give the avg).
>
> All statistics are done per lock class, per write (exclusive state)
> and per read (shared state).
>
> The statistics are collected per-cpu, so that the collection overhead
> is minimized via having no global cachemisses.
>
> This new lock statistics feature is independent of the lock dependency
> checking traditionally done by lockdep; it just shares the lock
> tracking code. It is also possible to enable both and runtime disabled
> either component - thereby avoiding the O(n^2) lock chain walks for
> instance.
really nice changes! The wait-time and hold-time changes should make it
as capable as lockmeter and more: lockmeter only measured spinlocks,
while your approach covers all lock types (spinlocks, rwlocks and
mutexes).
The performance enhancements in -v2 should make it much more scalable
than your first version was. (in fact i think it should be completely
scalable as the statistics counters are all per-cpu, so there should be
no cacheline bouncing at all from this)
Also, you've detached it from CONFIG_PROVE_LOCKING so the
lock-dependency overhead should be gone too.
Looks really good to me!
Acked-by: Ingo Molnar <[email protected]>
Ingo
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