linux-kernel - Re: [PATCH v2 2/2] perf stat: Stop repeating when ref_perf

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Message-ID:
 <GV1PR08MB105210E217DA914A0CA8989B4FB652@GV1PR08MB10521.eurprd08.prod.outlook.com>
Date: Fri, 13 Sep 2024 09:15:13 +0000
From: Yeo Reum Yun <YeoReum.Yun@....com>
To: James Clark <james.clark@...aro.org>
CC: nd <nd@....com>, "linux-perf-users@...r.kernel.org"
	<linux-perf-users@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "peterz@...radead.org"
	<peterz@...radead.org>, "mingo@...hat.com" <mingo@...hat.com>,
	"acme@...nel.org" <acme@...nel.org>, "namhyung@...nel.org"
	<namhyung@...nel.org>, Mark Rutland <Mark.Rutland@....com>,
	"alexander.shishkin@...ux.intel.com" <alexander.shishkin@...ux.intel.com>,
	"jolsa@...nel.org" <jolsa@...nel.org>, "irogers@...gle.com"
	<irogers@...gle.com>, "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
	"asmadeus@...ewreck.org" <asmadeus@...ewreck.org>
Subject: Re: [PATCH v2 2/2] perf stat: Stop repeating when ref_perf_stat()
 returns -1

Hi James.

> There's something wrong with the formatting here.

Oh. Sorry :(.. I'll fix it.

> But I don't think the comment answers my question about the other return
> codes. It just states what the code does.

> There are many more return -1's than just for COUNTER_FATAL, so it's not
> just that situation anyway. And in addition to that, there is -ENOMEM
> and others that aren't -1 which aren't explained that they are
> deliberately explicit retry or ignores.

Ah. not only STAT_RECORD error, it could be generated by pre/post command...
Okay. then I 'll changed with < 0. That would be better
and remove the comments.




________________________________________
From: James Clark <james.clark@...aro.org>
Sent: 13 September 2024 09:36
To: Yeo Reum Yun
Cc: nd; linux-perf-users@...r.kernel.org; linux-kernel@...r.kernel.org; peterz@...radead.org; mingo@...hat.com; acme@...nel.org; namhyung@...nel.org; Mark Rutland; alexander.shishkin@...ux.intel.com; jolsa@...nel.org; irogers@...gle.com; adrian.hunter@...el.com; asmadeus@...ewreck.org
Subject: Re: [PATCH v2 2/2] perf stat: Stop repeating when ref_perf_stat() returns -1



On 13/09/2024 03:02, Levi Yun wrote:
> Exit when run_perf_stat() returns an error to avoid continuously
> repeating the same error message. It's not expected that COUNTER_FATAL
> or internal errors are recoverable so there's no point in retrying.
>
> This fixes the following flood of error messages for permission issues,
> for example when perf_event_paranoid==3:
>    perf stat -r 1044 -- false
>
>    Error:
>    Access to performance monitoring and observability operations is limited.
>    ...
>    Error:
>    Access to performance monitoring and observability operations is limited.
>    ...
>    (repeating for 1044 times).
>
> Signed-off-by: Levi Yun <yeoreum.yun@....com>
> ---
> Changes in v2:
>    - Add some comments.
> ---
>   tools/perf/builtin-stat.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 954eb37ce7b8..0153925f2382 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -2875,7 +2875,15 @@ int cmd_stat(int argc, const char **argv)
>                       evlist__reset_prev_raw_counts(evsel_list);
>
>               status = run_perf_stat(argc, argv, run_idx);
> -             if (forever && status != -1 && !interval) {
> +             /*
> +              * * Meet COUNTER_FATAL situation (i.e) can't open event counter.
> +              * * In this case, there is a high chance of failure in the next attempt
> +              * * as well with the same reason. so, stop it.
> +              * */

There's something wrong with the formatting here.

But I don't think the comment answers my question about the other return
codes. It just states what the code does.

There are many more return -1's than just for COUNTER_FATAL, so it's not
just that situation anyway. And in addition to that, there is -ENOMEM
and others that aren't -1 which aren't explained that they are
deliberately explicit retry or ignores.

> +             if (status == -1)
> +                     break;
> +
> +             if (forever && !interval) {
>                       print_counters(NULL, argc, argv);
>                       perf_stat__reset_stats();
>               }
> --
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
>