linux-kernel - Re: [PATCH 2/2] perf stat: fix unexpected delay behaviour

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20220801114558.GB73228@leoy-ThinkPad-X240s>
Date:   Mon, 1 Aug 2022 19:45:58 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Adrián Herrera Arcila <adrian.herrera@....com>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, songliubraving@...com,
        james.clark@....com
Subject: Re: [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@....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@...aro.org>
Tested-by: Leo Yan <leo.yan@...aro.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.