Re: [RFC PATCH] perf sched latency: Add histogram and time interval options

[Aaron Tomlin]

On Fri, Jul 24, 2026 at 04:27:07PM -0700, Ian Rogers wrote:
> On Fri, Jul 24, 2026 at 1:12 PM Aaron Tomlin <atomlin@xxxxxxxxxxx> wrote:
> >
> > While 'perf sched latency' reports task runtime and delay statistics
> > (average and maximum delay), it does not provide a visual representation
> > of how task wait times are distributed across latency ranges between
> > snapshots (start and finish of the analysis window).
> >
> > The --histogram option collects CPU wait latencies (time between when
> > a task becomes runnable and when it gets scheduled onto a CPU) into 22
> > latency buckets, displaying an ASCII bar chart distribution.
> >
> > The --hist-mode option configures the bucketing scheme:
> >   - log (default). Logarithmic latency buckets ranging from
> >     sub-microsecond (< 1 us) up to >= 1.05 seconds
> >
> >   - linear. Equal-width linear latency buckets
> >     (i.e., 100 us steps up to >= 2.1 ms)
> >
> > The --time option allows filtering trace event processing to a
> > specific time interval [start,stop].
> >
> > Example histogram output excerpt:
> >
> >     ❯ sudo perf sched latency --histogram --CPU 0
> >
> >      CPU Wait Latency Distribution Histogram (between snapshots) (total samples: 36114)
> >      -------------------------------------------------------------------
> >       Latency Range    |      Count |    Pct | Histogram Graph
> >      -------------------------------------------------------------------
> >       < 1 us           |         17 |   0.0% | #
> >       2 - 4 us         |        673 |   1.9% | #
> >       4 - 8 us         |       6237 |  17.3% | ######
> >       8 - 16 us        |       3224 |   8.9% | ###
> >       16 - 32 us       |       1388 |   3.8% | #
> >       32 - 64 us       |        709 |   2.0% | #
> >       64 - 128 us      |        690 |   1.9% | #
> >       128 - 256 us     |        789 |   2.2% | #
> >       256 - 512 us     |        541 |   1.5% | #
> >       512 - 1024 us    |       2256 |   6.2% | ##
> >       1 - 2 ms         |       3577 |   9.9% | ###
> >       2 - 4 ms         |      13259 |  36.7% | ##############
> >       4 - 8 ms         |       2523 |   7.0% | ##
> >       8 - 16 ms        |        222 |   0.6% | #
> >       16 - 32 ms       |         10 |   0.0% | #
> >       >= 1.05 s        |          3 |   0.0% | #
> >      -------------------------------------------------------------------
> >
> > Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxxx>
> 
> This looks like a useful addition and because the behavior is behind a
> flag it won't break anyone. I saw Sashiko had some issues, but I'd be
> happy to add my tags once that's cleaned up.
> 
> Thanks,

Hi Ian,

Thank you for your feedback.

Understood.

Kind regards,
-- 
Aaron Tomlin