linux-kernel - Re: [PATCH v4] perf sched timehist: Add pre-migration wait time option

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Message-ID: <2b219313-f2ac-4228-b61f-f629d99c4a55@linux.ibm.com>
Date: Fri, 4 Oct 2024 00:20:46 +0530
From: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Athira Rajeev
 <atrajeev@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
        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>, acme@...hat.com,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Subject: Re: [PATCH v4] perf sched timehist: Add pre-migration wait time
 option

Hi Namhyung,

On 03/10/24 22:28, Namhyung Kim wrote:
> On Thu, Oct 03, 2024 at 08:29:14AM +0530, Madadi Vineeth Reddy wrote:
>> pre-migration wait time is the time that a task unnecessarily spends
>> on the runqueue of a CPU but doesn't get switched-in there. In terms
>> of tracepoints, it is the time between sched:sched_wakeup and
>> sched:sched_migrate_task.

[snip]

>> @@ -2239,6 +2244,7 @@ static void timehist_update_runtime_stats(struct thread_runtime *r,
> 
> One last thing, please update the ASCII art in the function comment on
> timehist_update_runtime_stats() to contain dt_pre_mig as well.

Sure, will do that in v5. Thanks for the feedback.

Thanks,
Madadi Vineeth Reddy

> 
> Thanks,
> Namhyung
> 
> 
>>  	r->dt_iowait  = 0;
>>  	r->dt_preempt = 0;
>>  	r->dt_run     = 0;
>> +	r->dt_pre_mig = 0;
>>  
>>  	if (tprev) {
>>  		r->dt_run = t - tprev;
>> @@ -2247,6 +2253,9 @@ static void timehist_update_runtime_stats(struct thread_runtime *r,
>>  				pr_debug("time travel: wakeup time for task > previous sched_switch event\n");
>>  			else
>>  				r->dt_delay = tprev - r->ready_to_run;
>> +
>> +			if ((r->migrated > r->ready_to_run) && (r->migrated < tprev))
>> +				r->dt_pre_mig = r->migrated - r->ready_to_run;
>>  		}
>>  
>>  		if (r->last_time > tprev)
>> @@ -2270,6 +2279,7 @@ static void timehist_update_runtime_stats(struct thread_runtime *r,
>>  	r->total_sleep_time   += r->dt_sleep;
>>  	r->total_iowait_time  += r->dt_iowait;
>>  	r->total_preempt_time += r->dt_preempt;
>> +	r->total_pre_mig_time += r->dt_pre_mig;
>>  }
>>  
>>  static bool is_idle_sample(struct perf_sample *sample,
>> @@ -2684,8 +2694,14 @@ static int timehist_migrate_task_event(const struct perf_tool *tool,
>>  
>>  	tr->migrations++;
>>  
>> +	if (tr->migrated == 0)
>> +		tr->migrated = sample->time;
>> +
>>  	/* show migrations if requested */
>> -	timehist_print_migration_event(sched, evsel, sample, machine, thread);
>> +	if (sched->show_migrations) {
>> +		timehist_print_migration_event(sched, evsel, sample,
>> +							machine, thread);
>> +	}
>>  
>>  	return 0;
>>  }
>> @@ -2836,11 +2852,13 @@ static int timehist_sched_change_event(const struct perf_tool *tool,
>>  		/* last state is used to determine where to account wait time */
>>  		tr->last_state = state;
>>  
>> -		/* sched out event for task so reset ready to run time */
>> +		/* sched out event for task so reset ready to run time and migrated time */
>>  		if (state == 'R')
>>  			tr->ready_to_run = t;
>>  		else
>>  			tr->ready_to_run = 0;
>> +
>> +		tr->migrated = 0;
>>  	}
>>  
>>  	evsel__save_time(evsel, sample->time, sample->cpu);
>> @@ -3280,8 +3298,8 @@ static int perf_sched__timehist(struct perf_sched *sched)
>>  		goto out;
>>  	}
>>  
>> -	if (sched->show_migrations &&
>> -	    perf_session__set_tracepoints_handlers(session, migrate_handlers))
>> +	if ((sched->show_migrations || sched->pre_migrations) &&
>> +		perf_session__set_tracepoints_handlers(session, migrate_handlers))
>>  		goto out;
>>  
>>  	/* pre-allocate struct for per-CPU idle stats */
>> @@ -3823,6 +3841,7 @@ int cmd_sched(int argc, const char **argv)
>>  	OPT_BOOLEAN(0, "show-prio", &sched.show_prio, "Show task priority"),
>>  	OPT_STRING(0, "prio", &sched.prio_str, "prio",
>>  		   "analyze events only for given task priority(ies)"),
>> +	OPT_BOOLEAN('P', "pre-migrations", &sched.pre_migrations, "Show pre-migration wait time"),
>>  	OPT_PARENT(sched_options)
>>  	};
>>  
>> -- 
>> 2.43.2
>>