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SubjectRe: [PATCH 2/2] perf stat: fix unexpected delay behaviour
On Fri, Jul 29, 2022 at 04:12:44PM +0000, Adrián Herrera Arcila wrote:
> The described --delay behaviour is to delay the enablement of events, but
> not the execution of the command, if one is passed, which is incorrectly
> the current behaviour.
>
> This patch decouples the enablement from the delay, and enables events
> before or after launching the workload dependent on the options passed
> by the user. This code structure is inspired by that in perf-record, and
> tries to be consistent with it.
>
> Link: https://lore.kernel.org/linux-perf-users/7BFD066E-B0A8-49D4-B635-379328F0CF4C@fb.com
> Fixes: d0a0a511493d ("perf stat: Fix forked applications enablement of counters")
> Signed-off-by: Adrián Herrera Arcila <adrian.herrera@arm.com>

bpf_counter() is not enabled for delay in this patch, but I think this
is purposed to keep the same behaviour with before. I would leave it
to Song for a call.

The patch LGTM and I tested with commands:

$ time ./perf stat --delay 2000 --quiet sleep 2
Events disabled
Events enabled

real 0m2.039s
user 0m0.007s
sys 0m0.016s

$ ./perf stat --delay 2000 --quiet echo "marking"
Events disabled
marking
Events enabled

Reviewed-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Leo Yan <leo.yan@linaro.org>

P.s. I took a bit time to get clear how 'perf stat' set enable_on_exec
flag, which is set in the function create_perf_stat_counter(), so this
can enable PMU event for the case when delay is zero, and this can
avoid losing PMU tracing for workload.

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