Re: [PATCH v4 2/9] perf record --off-cpu: Add --off-cpu-thresh

[Namhyung Kim <namhyung@kernel.org>]

On Wed, Aug 07, 2024 at 11:38:36PM +0800, Howard Chu wrote:
> Add the --off-cpu-thresh argument to specify the off-cpu time threshold.
> If the off-cpu time exceeds this threshold, dump the off-cpu data
> directly.
> 
> Suggested-by: Ian Rogers <irogers@google.com>
> Signed-off-by: Howard Chu <howardchu95@gmail.com>
> ---
>  tools/perf/builtin-record.c            | 26 ++++++++++++++++++++++++++
>  tools/perf/util/bpf_off_cpu.c          |  2 ++
>  tools/perf/util/bpf_skel/off_cpu.bpf.c |  2 ++
>  tools/perf/util/record.h               |  1 +
>  4 files changed, 31 insertions(+)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 72345d1e54b0..60c6fe7b4804 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -3133,6 +3133,28 @@ 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 = strtoul(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)
>  {
>  }
> @@ -3326,6 +3348,7 @@ static struct record record = {
>  		.ctl_fd              = -1,
>  		.ctl_fd_ack          = -1,
>  		.synth               = PERF_SYNTH_ALL,
> +		.off_cpu_thresh      = OFF_CPU_THRESH_DEFAULT,

Where is it defined?

Thanks,
Namhyung


>  	},
>  	.tool = {
>  		.sample		= process_sample_event,
> @@ -3560,6 +3583,9 @@ 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 microseconds. (default: 500000)",
> +		     record__parse_off_cpu_thresh),
>  	OPT_END()
>  };
>  
> diff --git a/tools/perf/util/bpf_off_cpu.c b/tools/perf/util/bpf_off_cpu.c
> index 6af36142dc5a..1e0e454bfb5e 100644
> --- a/tools/perf/util/bpf_off_cpu.c
> +++ b/tools/perf/util/bpf_off_cpu.c
> @@ -272,6 +272,8 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
>  		}
>  	}
>  
> +	skel->bss->offcpu_thresh = opts->off_cpu_thresh * 1000ull;
> +
>  	err = off_cpu_bpf__attach(skel);
>  	if (err) {
>  		pr_err("Failed to attach off-cpu BPF skeleton\n");
> diff --git a/tools/perf/util/bpf_skel/off_cpu.bpf.c b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> index d877a0a9731f..cca1b6990a57 100644
> --- a/tools/perf/util/bpf_skel/off_cpu.bpf.c
> +++ b/tools/perf/util/bpf_skel/off_cpu.bpf.c
> @@ -96,6 +96,8 @@ const volatile bool uses_cgroup_v1 = false;
>  
>  int perf_subsys_id = -1;
>  
> +__u64 sample_id, sample_type, offcpu_thresh;
> +
>  /*
>   * Old kernel used to call it task_struct->state and now it's '__state'.
>   * Use BPF CO-RE "ignored suffix rule" to deal with it like below:
> 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;
>  };
>  
>  extern const char * const *record_usage;
> -- 
> 2.45.2
>