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Date:   Mon, 1 Aug 2022 19:45:58 +0800
From:   Leo Yan <leo.yan@linaro.org>
To:     =?iso-8859-1?Q?Adri=E1n?= Herrera Arcila <adrian.herrera@arm.com>
Cc:     linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        acme@kernel.org, peterz@infradead.org, mingo@redhat.com,
        mark.rutland@arm.com, alexander.shishkin@linux.intel.com,
        jolsa@kernel.org, namhyung@kernel.org, songliubraving@fb.com,
        james.clark@arm.com
Subject: Re: [PATCH 2/2] perf stat: fix unexpected delay behaviour
Message-ID: <20220801114558.GB73228@leoy-ThinkPad-X240s>
References: <20220729161244.10522-1-adrian.herrera@arm.com>
 <20220729161244.10522-2-adrian.herrera@arm.com>
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On Fri, Jul 29, 2022 at 04:12:44PM +0000, Adri?n 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: Adri?n 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.