linux-kernel - Re: [PATCH v1 04/12] perf parse-events: Allow the cpu term to be a PMU

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Message-ID: <aHgG-9iuoj4B72SU@google.com>
Date: Wed, 16 Jul 2025 13:09:31 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Thomas Falcon <thomas.falcon@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Ben Gainey <ben.gainey@....com>,
	James Clark <james.clark@...aro.org>,
	Howard Chu <howardchu95@...il.com>,
	Weilin Wang <weilin.wang@...el.com>, Levi Yun <yeoreum.yun@....com>,
	"Dr. David Alan Gilbert" <linux@...blig.org>,
	Zhongqiu Han <quic_zhonhan@...cinc.com>,
	Blake Jones <blakejones@...gle.com>,
	Yicong Yang <yangyicong@...ilicon.com>,
	Anubhav Shelat <ashelat@...hat.com>,
	Thomas Richter <tmricht@...ux.ibm.com>,
	Jean-Philippe Romain <jean-philippe.romain@...s.st.com>,
	Song Liu <song@...nel.org>, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 04/12] perf parse-events: Allow the cpu term to be a
 PMU

On Fri, Jun 27, 2025 at 12:24:09PM -0700, Ian Rogers wrote:
> On hybrid systems, events like msr/tsc/ will aggregate counts across
> all CPUs. Often metrics only want a value like msr/tsc/ for the cores
> on which the metric is being computed. Listing each CPU with terms
> cpu=0,cpu=1.. is laborious and would need to be encoded for all
> variations of a CPU model.
> 
> Allow the cpumask from a PMU to be an argument to the cpu term. For
> example in the following the cpumask of the cstate_pkg PMU selects the
> CPUs to count msr/tsc/ counter upon:
> ```
> $ cat /sys/bus/event_source/devices/cstate_pkg/cpumask
> 0
> $ perf stat -A -e 'msr/tsc,cpu=cstate_pkg/' -a sleep 0.1

It can be confusing if 'cpu' takes a number or a PMU name.  What about
adding a new term (maybe 'cpu_from') to handle this case?

Also please update the documentation.

Thanks,
Namhyung

> 
>  Performance counter stats for 'system wide':
> 
> CPU0          252,621,253      msr/tsc,cpu=cstate_pkg/
> 
>        0.101184092 seconds time elapsed
> ```
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/parse-events.c | 37 +++++++++++++++++++++++++---------
>  1 file changed, 28 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 7a32d5234a64..ef38eb082342 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -192,10 +192,20 @@ static struct perf_cpu_map *get_config_cpu(const struct parse_events_terms *head
>  
>  	list_for_each_entry(term, &head_terms->terms, list) {
>  		if (term->type_term == PARSE_EVENTS__TERM_TYPE_CPU) {
> -			struct perf_cpu_map *cpu = perf_cpu_map__new_int(term->val.num);
> +			struct perf_cpu_map *term_cpus;
>  
> -			perf_cpu_map__merge(&cpus, cpu);
> -			perf_cpu_map__put(cpu);
> +			if (term->type_val == PARSE_EVENTS__TERM_TYPE_NUM) {
> +				term_cpus = perf_cpu_map__new_int(term->val.num);
> +			} else {
> +				struct perf_pmu *pmu = perf_pmus__find(term->val.str);
> +
> +				if (perf_cpu_map__is_empty(pmu->cpus))
> +					term_cpus = pmu->is_core ? cpu_map__online() : NULL;
> +				else
> +					term_cpus = perf_cpu_map__get(pmu->cpus);
> +			}
> +			perf_cpu_map__merge(&cpus, term_cpus);
> +			perf_cpu_map__put(term_cpus);
>  		}
>  	}
>  
> @@ -1054,12 +1064,21 @@ do {									   \
>  		}
>  		break;
>  	case PARSE_EVENTS__TERM_TYPE_CPU:
> -		CHECK_TYPE_VAL(NUM);
> -		if (term->val.num >= (u64)cpu__max_present_cpu().cpu) {
> -			parse_events_error__handle(err, term->err_val,
> -						strdup("too big"),
> -						NULL);
> -			return -EINVAL;
> +		if (term->type_val == PARSE_EVENTS__TERM_TYPE_NUM) {
> +			if (term->val.num >= (u64)cpu__max_present_cpu().cpu) {
> +				parse_events_error__handle(err, term->err_val,
> +							strdup("too big"),
> +							/*help=*/NULL);
> +				return -EINVAL;
> +			}
> +		} else {
> +			assert(term->type_val == PARSE_EVENTS__TERM_TYPE_STR);
> +			if (perf_pmus__find(term->val.str) == NULL) {
> +				parse_events_error__handle(err, term->err_val,
> +							strdup("not a valid PMU"),
> +							/*help=*/NULL);
> +				return -EINVAL;
> +			}
>  		}
>  		break;
>  	case PARSE_EVENTS__TERM_TYPE_DRV_CFG:
> -- 
> 2.50.0.727.gbf7dc18ff4-goog
>