Re: [PATCH v7 01/10] perf record --off-cpu: Add --off-cpu-thresh option
From: Ian Rogers
Date: Mon Nov 11 2024 - 12:42:38 EST
On Fri, Nov 8, 2024 at 12:41 PM Howard Chu <howardchu95@xxxxxxxxx> wrote:
>
> Specify the threshold for dumping offcpu samples with --off-cpu-thresh,
> the unit is us (microsecond). Default value is 500000us (500ms, 0.5s).
>
> Suggested-by: Ian Rogers <irogers@xxxxxxxxxx>
> Signed-off-by: Howard Chu <howardchu95@xxxxxxxxx>
> ---
> tools/perf/builtin-record.c | 26 ++++++++++++++++++++++++++
> tools/perf/util/off_cpu.h | 1 +
> tools/perf/util/record.h | 1 +
> 3 files changed, 28 insertions(+)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index f83252472921..ee04fdd7f2ca 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;
> +
> + if (!str)
> + return -EINVAL;
> +
> + off_cpu_thresh = strtoull(str, &endptr, 10);
> +
> + /* threshold isn't string "0", yet strtoull() returns 0, parsing failed */
> + if (*endptr || (off_cpu_thresh == 0 && strcmp(str, "0")))
> + return -EINVAL;
> + else
> + opts->off_cpu_thresh = off_cpu_thresh;
> +
> + 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 = 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..3c11416e6627 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;
nit: I know existing style doesn't do this but it would be nice if
this were off_cpu_thresh_us (ie the unit is at the end of the variable
name). Most programming languages have gone for having explicit
time/duration types to remove ambiguity. We're peasants so it'd be
nice if the variable name were hinting me in the write direction.
Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
Thanks,
Ian
> };
>
> extern const char * const *record_usage;
> --
> 2.43.0
>