On Tue, Aug 30, 2022 at 02:49:16PM -0700, Suren Baghdasaryan wrote:

From: Kent Overstreet <kent.overstreet@linux.dev>

This adds the ability to easily instrument code for measuring latency.
To use, add the following to calls to your code, at the start and end of
the event you wish to measure:

  code_tag_time_stats_start(start_time);
  code_tag_time_stats_finish(start_time);

Stastistics will then show up in debugfs under
/sys/kernel/debug/time_stats, listed by file and line number.

Stastics measured include weighted averages of frequency, duration, max
duration, as well as quantiles.

This patch also instruments all calls to init_wait and finish_wait,
which includes all calls to wait_event. Example debugfs output:

How can't you do this with a simple eBPF script on top of
trace_sched_stat_* and friends?