Re: [PATCH v2 RESEND] perf/lock: enable end-timestamp accounting for cgroup aggregation

[Namhyung Kim <namhyung@kernel.org>]

On Thu, Jun 04, 2026 at 10:37:05AM -0300, Arnaldo Carvalho de Melo wrote:
> On Sun, May 31, 2026 at 01:29:40AM +0530, Suchit Karunakaran wrote:
> > update_lock_stat() handles lock contentions that start but never reach a
> > contention_end event (e.g., locks still held when profiling stops), but
> > previously treated LOCK_AGGR_CGROUP as a no-op due to missing cgroup
> > context in userspace.
> > 
> > Fix this by adding a cgroup_id field to struct tstamp_data, recording it
> > at contention_begin using get_current_cgroup_id() when aggr_mode is
> > LOCK_AGGR_CGROUP. Capturing it at contention_begin is semantically
> > correct, the contention cost is incurred by the task that had to wait,
> > not by whatever task happens to be running at contention_end. It is also
> > preferable from a performance standpoint, as contention_end runs just
> > before the task enters the critical section.
> > 
> > Update contention_end to use pelem->cgroup_id instead of calling
> > get_current_cgroup_id() dynamically, ensuring both complete and
> > incomplete contention events attribute the wait time to the cgroup at
> > wait-start time consistently.
> 
> Namhyung, can you provide an Acked-by or Reviewed-by?

Reviewed-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung