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Message-ID: <Z1eGw52LThYh1Gjx@google.com>
Date: Mon, 9 Dec 2024 16:09:39 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Howard Chu <howardchu95@...il.com>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
mark.rutland@....com, alexander.shishkin@...ux.intel.com,
jolsa@...nel.org, irogers@...gle.com, adrian.hunter@...el.com,
kan.liang@...ux.intel.com, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org,
Arnaldo Carvalho de Melo <acme@...hat.com>,
James Clark <james.clark@...aro.org>
Subject: Re: [PATCH v9 01/10] perf record --off-cpu: Add --off-cpu-thresh
option
Hi Howard,
Sorry for the late review.
On Thu, Nov 21, 2024 at 08:38:31PM -0800, Howard Chu wrote:
> Specify the threshold for dumping offcpu samples with --off-cpu-thresh,
> the unit is us (microsecond). Default value is 500,000us (500ms, 0.5s).
I guess we mostly care about more than milli-seconds of off-cpu times.
Can we change the unit to msec?
Also I think this commit can be moved to later in this series - like
after implementing direct offcpu samples. If I see the commit in
history later, I'd think it works. But it's not at this point.
Otherwise, looks all good to me. :)
Thanks,
Namhyung
>
> Example:
>
> perf record --off-cpu --off-cpu-thresh 400000
>
> The example above collects off-cpu samples whose off-cpu time is longer
> than 400,000us
>
> Suggested-by: Ian Rogers <irogers@...gle.com>
> Suggested-by: Namhyung Kim <namhyung@...nel.org>
> Suggested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> Reviewed-by: Ian Rogers <irogers@...gle.com>
> Signed-off-by: Howard Chu <howardchu95@...il.com>
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: James Clark <james.clark@...aro.org>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Kan Liang <kan.liang@...ux.intel.com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Link: https://lore.kernel.org/r/20241108204137.2444151-2-howardchu95@gmail.com
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
> tools/perf/Documentation/perf-record.txt | 9 ++++++++
> tools/perf/builtin-record.c | 26 ++++++++++++++++++++++++
> tools/perf/util/off_cpu.h | 1 +
> tools/perf/util/record.h | 1 +
> 4 files changed, 37 insertions(+)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 242223240a08..05c8977983de 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -829,6 +829,15 @@ filtered through the mask provided by -C option.
> only, as of now. So the applications built without the frame
> pointer might see bogus addresses.
>
> + off-cpu profiling consists two types of samples: direct samples, which
> + share the same behavior as regular samples, and the accumulated
> + samples, stored in BPF stack trace map, presented after all the regular
> + samples.
> +
> +--off-cpu-thresh::
> + Once a task's off-cpu time reaches this threshold, it generates a
> + direct off-cpu sample.
> +
> --setup-filter=<action>::
> Prepare BPF filter to be used by regular users. The action should be
> either "pin" or "unpin". The filter can be used after it's pinned.
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index f83252472921..c069000efe5c 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -3149,6 +3149,28 @@ static int record__parse_mmap_pages(const struct option *opt,
> return ret;
> }
>
> +static int record__parse_off_cpu_thresh(const struct option *opt,
> + const char *str,
> + int unset __maybe_unused)
> +{
> + struct record_opts *opts = opt->value;
> + char *endptr;
> + u64 off_cpu_thresh_us;
> +
> + if (!str)
> + return -EINVAL;
> +
> + off_cpu_thresh_us = strtoull(str, &endptr, 10);
> +
> + /* threshold isn't string "0", yet strtoull() returns 0, parsing failed */
> + if (*endptr || (off_cpu_thresh_us == 0 && strcmp(str, "0")))
> + return -EINVAL;
> + else
> + opts->off_cpu_thresh_us = off_cpu_thresh_us;
> +
> + return 0;
> +}
> +
> void __weak arch__add_leaf_frame_record_opts(struct record_opts *opts __maybe_unused)
> {
> }
> @@ -3342,6 +3364,7 @@ static struct record record = {
> .ctl_fd = -1,
> .ctl_fd_ack = -1,
> .synth = PERF_SYNTH_ALL,
> + .off_cpu_thresh_us = OFFCPU_THRESH,
> },
> };
>
> @@ -3564,6 +3587,9 @@ static struct option __record_options[] = {
> OPT_BOOLEAN(0, "off-cpu", &record.off_cpu, "Enable off-cpu analysis"),
> OPT_STRING(0, "setup-filter", &record.filter_action, "pin|unpin",
> "BPF filter action"),
> + OPT_CALLBACK(0, "off-cpu-thresh", &record.opts, "us",
> + "Dump off-cpu samples if off-cpu time reaches this threshold. The unit is microsecond (default: 500000)",
> + record__parse_off_cpu_thresh),
> OPT_END()
> };
>
> diff --git a/tools/perf/util/off_cpu.h b/tools/perf/util/off_cpu.h
> index 2dd67c60f211..c6edc0f7c40d 100644
> --- a/tools/perf/util/off_cpu.h
> +++ b/tools/perf/util/off_cpu.h
> @@ -16,6 +16,7 @@ struct record_opts;
> PERF_SAMPLE_PERIOD | PERF_SAMPLE_CALLCHAIN | \
> PERF_SAMPLE_CGROUP)
>
> +#define OFFCPU_THRESH 500000ull
>
> #ifdef HAVE_BPF_SKEL
> int off_cpu_prepare(struct evlist *evlist, struct target *target,
> diff --git a/tools/perf/util/record.h b/tools/perf/util/record.h
> index a6566134e09e..2ca74add26c0 100644
> --- a/tools/perf/util/record.h
> +++ b/tools/perf/util/record.h
> @@ -79,6 +79,7 @@ struct record_opts {
> int synth;
> int threads_spec;
> const char *threads_user_spec;
> + u64 off_cpu_thresh_us;
> };
>
> extern const char * const *record_usage;
> --
> 2.43.0
>
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