[0/2,v2] memcg: tracepoint for flushing stats

Message

JP Kobryn Oct. 26, 2024, 12:48 a.m. UTC

This tracepoint gives visibility on how often the flushing of memcg stats
occurs and contains info on whether it was forced, skipped, and the value
of stats updated. It can help with understanding how readers are affected
by having to perform the flush, and the effectiveness of the flush by
inspecting the number of stats updated. Paired with the recently added
tracepoints for tracing rstat updates, it can also help show correlation
where stats exceed thresholds frequently.

JP Kobryn (2):
  add memcg flush tracepoint event
  use memcg flush tracepoint

 include/trace/events/memcg.h | 25 +++++++++++++++++++++++++
 mm/memcontrol.c              | 22 +++++++++++++---------
 2 files changed, 38 insertions(+), 9 deletions(-)

Comments

Yosry Ahmed Oct. 26, 2024, 6:36 a.m. UTC | #1

On Fri, Oct 25, 2024 at 5:48 PM JP Kobryn <[e-mail]> wrote:
>
> This tracepoint gives visibility on how often the flushing of memcg stats
> occurs and contains info on whether it was forced, skipped, and the value
> of stats updated. It can help with understanding how readers are affected
> by having to perform the flush, and the effectiveness of the flush by
> inspecting the number of stats updated. Paired with the recently added
> tracepoints for tracing rstat updates, it can also help show correlation
> where stats exceed thresholds frequently.
>
> JP Kobryn (2):
>   add memcg flush tracepoint event
>   use memcg flush tracepoint

I think this should be re-arranged. The first patch should have the
refactoring of the flushing code with no functional changes. The
second patch would introduce the tracepoint and use it.

Also, please use more descriptive commit logs. Most of the text in the
cover letter should be in the patch adding the tracepoint. For the
refactoring patch, please describe the refactoring and its purpose,
and mention that it is expected to be functionally a noop.

>
>  include/trace/events/memcg.h | 25 +++++++++++++++++++++++++
>  mm/memcontrol.c              | 22 +++++++++++++---------
>  2 files changed, 38 insertions(+), 9 deletions(-)
>
> --
> 2.47.0
>