linux-kernel - Re: [PATCH v3 5/8] perf sched stats: Add support for live mode

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Message-ID: <01671eda-c8f3-4093-a782-2c73b4a73b12@amd.com>
Date: Mon, 24 Mar 2025 14:45:51 +0530
From: "Sapkal, Swapnil" <swapnil.sapkal@....com>
To: Namhyung Kim <namhyung@...nel.org>
CC: <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
	<irogers@...gle.com>, <james.clark@....com>, <ravi.bangoria@....com>,
	<yu.c.chen@...el.com>, <mark.rutland@....com>,
	<alexander.shishkin@...ux.intel.com>, <jolsa@...nel.org>,
	<rostedt@...dmis.org>, <vincent.guittot@...aro.org>,
	<adrian.hunter@...el.com>, <kan.liang@...ux.intel.com>,
	<gautham.shenoy@....com>, <kprateek.nayak@....com>, <juri.lelli@...hat.com>,
	<yangjihong@...edance.com>, <void@...ifault.com>, <tj@...nel.org>,
	<sshegde@...ux.ibm.com>, <linux-kernel@...r.kernel.org>,
	<linux-perf-users@...r.kernel.org>, <santosh.shukla@....com>,
	<ananth.narayan@....com>, <sandipan.das@....com>, James Clark
	<james.clark@...aro.org>
Subject: Re: [PATCH v3 5/8] perf sched stats: Add support for live mode

Hi Namhyung,

Sorry for the delay in response.

On 3/15/2025 10:16 AM, Namhyung Kim wrote:
> On Tue, Mar 11, 2025 at 12:02:27PM +0000, Swapnil Sapkal wrote:
>> The live mode works similar to simple `perf stat` command, by profiling
>> the target and printing results on the terminal as soon as the target
>> finishes.
>>
>> Example usage:
>>
>>    # perf sched stats -- sleep 10
>>
>> Co-developed-by: Ravi Bangoria <ravi.bangoria@....com>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
>> Tested-by: James Clark <james.clark@...aro.org>
>> Signed-off-by: Swapnil Sapkal <swapnil.sapkal@....com>
>> ---
>>   tools/perf/builtin-sched.c | 87 +++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 86 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
>> index e2e7dbc4f0aa..9813e25b54b8 100644
>> --- a/tools/perf/builtin-sched.c
>> +++ b/tools/perf/builtin-sched.c
>> @@ -4364,6 +4364,91 @@ static int perf_sched__schedstat_report(struct perf_sched *sched)
>>   	return err;
>>   }
>>   
>> +static int process_synthesized_event_live(const struct perf_tool *tool __maybe_unused,
>> +					  union perf_event *event,
>> +					  struct perf_sample *sample __maybe_unused,
>> +					  struct machine *machine __maybe_unused)
>> +{
>> +	return perf_sched__process_schedstat(NULL, event);
>> +}
>> +
>> +static int perf_sched__schedstat_live(struct perf_sched *sched,
>> +				      int argc, const char **argv)
>> +{
>> +	struct evlist *evlist;
>> +	struct target *target;
>> +	int reset = 0;
>> +	int err = 0;
>> +
>> +	signal(SIGINT, sighandler);
>> +	signal(SIGCHLD, sighandler);
>> +	signal(SIGTERM, sighandler);
>> +
>> +	evlist = evlist__new();
>> +	if (!evlist)
>> +		return -ENOMEM;
>> +
>> +	/*
>> +	 * `perf sched schedstat` does not support workload profiling (-p pid)
>> +	 * since /proc/schedstat file contains cpu specific data only. Hence, a
>> +	 * profile target is either set of cpus or systemwide, never a process.
>> +	 * Note that, although `-- <workload>` is supported, profile data are
>> +	 * still cpu/systemwide.
>> +	 */
>> +	target = zalloc(sizeof(struct target));
> 
> As I said, you can put it on stack.
> 

Sure.

> 
>> +	if (cpu_list)
>> +		target->cpu_list = cpu_list;
>> +	else
>> +		target->system_wide = true;
>> +
>> +	if (argc) {
>> +		err = evlist__prepare_workload(evlist, target, argv, false, NULL);
>> +		if (err)
>> +			goto out_target;
>> +	}
>> +
>> +	if (cpu_list) {
>> +		user_requested_cpus = perf_cpu_map__new(cpu_list);
>> +		if (!user_requested_cpus)
>> +			goto out_target;
>> +	}
> 
> How about this instead?
> 
> 	evlist__create_maps(evlist, target);
> 

Sure, will use evlist__create_maps(evlist, target).

>> +
>> +	err = perf_event__synthesize_schedstat(&(sched->tool),
>> +					       process_synthesized_event_live,
>> +					       user_requested_cpus);
>> +	if (err < 0)
>> +		goto out_target;
>> +
>> +	err = enable_sched_schedstats(&reset);
>> +	if (err < 0)
>> +		goto out_target;
>> +
>> +	if (argc)
>> +		evlist__start_workload(evlist);
>> +
>> +	/* wait for signal */
>> +	pause();
>> +
>> +	if (reset) {
>> +		err = disable_sched_schedstat();
>> +		if (err < 0)
>> +			goto out_target;
>> +	}
>> +
>> +	err = perf_event__synthesize_schedstat(&(sched->tool),
>> +					       process_synthesized_event_live,
>> +					       user_requested_cpus);
>> +	if (err)
>> +		goto out_target;
>> +
>> +	setup_pager();
>> +	show_schedstat_data(cpu_head);
>> +	free_schedstat(cpu_head);
>> +out_target:
>> +	free(target);
> 
> 	evlist__delete(evlist);
> 
> and unless you use evlist__create_maps().
> 

Ack.

> 	perf_cpu_map__put(user_requested_cpus);
> 
> Thanks,
> Namhyung
> 
> 
>> +	return err;
>> +}
>> +
>>   static bool schedstat_events_exposed(void)
>>   {
>>   	/*
>> @@ -4686,7 +4771,7 @@ int cmd_sched(int argc, const char **argv)
>>   						     stats_usage, 0);
>>   			return perf_sched__schedstat_report(&sched);
>>   		}
>> -		usage_with_options(stats_usage, stats_options);
>> +		return perf_sched__schedstat_live(&sched, argc, argv);
>>   	} else {
>>   		usage_with_options(sched_usage, sched_options);
>>   	}
>> -- 
>> 2.43.0
>>
--
Thanks and Regards,
Swapnil