Re: [PATCH 2/2] perf tests: add test for trace output loss

[Howard Chu]

Hello,

On Thu, Nov 14, 2024 at 12:09 PM Arnaldo Carvalho de Melo
<acme@xxxxxxxxxx> wrote:
>
> On Thu, Nov 14, 2024 at 09:44:56AM -0800, Benjamin Peterson wrote:
> > > On Thu, Nov 14, 2024 at 02:37:52PM -0300, Arnaldo Carvalho de Melo wrote:
> > > diff --git a/tools/perf/tests/shell/trace_exit_race.sh b/tools/perf/tests/shell/trace_exit_race.sh
> > > index 8b70324bc5b4fb4c..c37ed6bb9f7e8fab 100755
> > > --- a/tools/perf/tests/shell/trace_exit_race.sh
> > > +++ b/tools/perf/tests/shell/trace_exit_race.sh
> > > @@ -12,10 +12,10 @@
> > >  skip_if_no_perf_trace || exit 2
>
> > >  trace_shutdown_race() {
> > > -       for i in $(seq 100); do
> > > +       for _ in $(seq 100); do
> > >                 perf trace -e syscalls:sys_enter_exit_group true 2>>$file
> > >         done
> > > -       [ $(grep -c -E " +[0-9]+\.[0-9]+ +true/[0-9]+ syscalls:sys_enter_exit_group\(\)$" $file) = "100" ]
> > > +       [ "$(grep -c -E ' +[0-9]+\.[0-9]+ +true/[0-9]+ syscalls:sys_enter_exit_group\(\)$' $file)" = "100" ]
> > >  }
>
> > This all looks okay.
>
> The test is failing for me as there is garbage in the output of perf
> trace even with Namhyung having already applied your previous patch:
>
> ⬢ [acme@toolbox perf-tools-next]$ git log --oneline --author benjamin@xxxxxxxxxxx
> 12bd434f68ea45c7 (HEAD -> perf-tools-next) perf tests: Add test for 'perf trace' output loss
> efbcd2cd7eac10a9 perf trace: Do not lose last events in a race
> 5fb8e56542a3cf46 (perf-tools-next/tmp.perf-tools-next) perf trace: avoid garbage when not printing a trace event's arguments
> ⬢ [acme@toolbox perf-tools-next]$
>
> root@number:~# perf trace -e syscalls:sys_enter_exit_group true
>      0.000 true/1982428 syscalls:sys_enter_exit_group( k?m)
> root@number:~# perf trace -e syscalls:sys_enter_exit_group true
>      0.000 true/1982430 syscalls:sys_enter_exit_group()
> root@number:~# perf trace -e syscalls:sys_enter_exit_group true
>      0.000 true/1982432 syscalls:sys_enter_exit_group()
> root@number:~# perf trace -e syscalls:sys_enter_exit_group true
>      0.000 true/1982434 syscalls:sys_enter_exit_group()
> root@number:~# perf trace -e syscalls:sys_enter_exit_group true
>      0.000 true/1982437 syscalls:sys_enter_exit_group( k�)
> root@number:~# perf trace -e syscalls:sys_enter_exit_group true
>      0.000 true/1982439 syscalls:sys_enter_exit_group(, loads 8��1)
> root@number:~#
>
> So we don't _miss_ the events, which I was noticing and brought me to
> test your latest 2 patches, which I applied and added a Tested-by, now
> tryint to figure out this garbage...

Benjamin has already sent v2 to fix this:
https://lore.kernel.org/linux-perf-users/20241107232128.108981-2-benjamin@xxxxxxxxxxx/

Thanks,
Howard

>
> - Arnaldo
>