linux-kernel - Re: [RESEND PATCH v1] perf stat: Enable ignore_missing

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Date:   Thu, 23 Jun 2022 11:49:42 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Gang Li <ligang.bdlg@...edance.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v1] perf stat: Enable ignore_missing_thread for
 stat

Em Wed, Jun 22, 2022 at 11:00:37AM +0800, Gang Li escreveu:
> perf already support ignore_missing_thread for -p, but not yet
> applied to `perf stat -p <pid>`. This patch enables ignore_missing_thread
> for `perf stat -p <pid>`.

Thanks, will add it and stick the original explanation about
ignore_missing_thread so that reviewers of this patch can get a
refresher:

>From  ca8000684ec4e66f965e1f9547a3c6cb834154ca
----------
    While monitoring a multithread process with pid option, perf sometimes
    may return sys_perf_event_open failure with 3(No such process) if any of
    the process's threads die before we open the event. However, we want
    perf continue monitoring the remaining threads and do not exit with
    error.
----------

Thanks,

- Arnaldo
 
> Signed-off-by: Gang Li <ligang.bdlg@...edance.com>
> ---
>  tools/perf/builtin-stat.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 4ce87a8eb7d7..d2ecd4d29624 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -2586,6 +2586,8 @@ int cmd_stat(int argc, const char **argv)
>  	if (evlist__initialize_ctlfd(evsel_list, stat_config.ctl_fd, stat_config.ctl_fd_ack))
>  		goto out;
>  
> +	/* Enable ignoring missing threads when -p option is defined. */
> +	evlist__first(evsel_list)->ignore_missing_thread = target.pid;
>  	status = 0;
>  	for (run_idx = 0; forever || run_idx < stat_config.run_count; run_idx++) {
>  		if (stat_config.run_count != 1 && verbose > 0)
> -- 
> 2.20.1

-- 

- Arnaldo