linux-kernel - Re: [PATCH] perf: sched map skips redundant lines with cpu filters

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Date: Sun, 16 Jun 2024 01:37:31 +0530
From: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
To: Fernand Sieber <sieberf@...zon.com>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Subject: Re: [PATCH] perf: sched map skips redundant lines with cpu filters

Hi Fernand,

On 14/06/24 13:05, Fernand Sieber wrote:
> perf sched map supports cpu filter.
> However, even with cpu filters active, any context switch currently
> corresponds to a separate line.
> As result, context switches on irrelevant cpus result to redundant lines,
> which makes the output particlularly difficult to read on wide
> architectures.
> 
> Fix it by skipping printing for irrelevant CPUs.
> 
> Example snippet of output before fix:
> 
>   *B0       1.461147 secs
>    B0
>    B0
>    B0
>   *G0       1.517139 secs
> 
> After fix:
> 
>   *B0       1.461147 secs
>   *G0       1.517139 secs

Yes, this makes sense. The current implementation doesn't even print timestamp
for the redundant lines as shown in the example below.

   .  *F0   708529.114889 secs F0 => schbench:278841
   .   F0 
   .   F0 
   .  *.    708529.114919 secs 

It makes sense to remove them entirely since we can still infer the sched-out
time for the selected CPUs implicitly.

Reviewed-and-tested-by: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>

Thanks and Regards
Madadi Vineeth Reddy

> 
> Signed-off-by: Fernand Sieber <sieberf@...zon.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> ---
>  tools/perf/builtin-sched.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index 7422c930abaf..aa59f763ca46 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -1594,8 +1594,6 @@ static int map_switch_event(struct perf_sched *sched, struct evsel *evsel,
>  
>  	sched->curr_thread[this_cpu.cpu] = thread__get(sched_in);
>  
> -	printf("  ");
> -
>  	new_shortname = 0;
>  	if (!tr->shortname[0]) {
>  		if (!strcmp(thread__comm_str(sched_in), "swapper")) {
> @@ -1622,6 +1620,11 @@ static int map_switch_event(struct perf_sched *sched, struct evsel *evsel,
>  		new_shortname = 1;
>  	}
>  
> +	if (sched->map.cpus && !perf_cpu_map__has(sched->map.cpus, this_cpu))
> +		goto out;
> +
> +	printf("  ");
> +
>  	for (i = 0; i < cpus_nr; i++) {
>  		struct perf_cpu cpu = {
>  			.cpu = sched->map.comp ? sched->map.comp_cpus[i].cpu : i,
> @@ -1656,9 +1659,6 @@ static int map_switch_event(struct perf_sched *sched, struct evsel *evsel,
>  			color_fprintf(stdout, color, "   ");
>  	}
>  
> -	if (sched->map.cpus && !perf_cpu_map__has(sched->map.cpus, this_cpu))
> -		goto out;
> -
>  	timestamp__scnprintf_usec(timestamp, stimestamp, sizeof(stimestamp));
>  	color_fprintf(stdout, color, "  %12s secs ", stimestamp);
>  	if (new_shortname || tr->comm_changed || (verbose > 0 && thread__tid(sched_in))) {
> @@ -1675,9 +1675,9 @@ static int map_switch_event(struct perf_sched *sched, struct evsel *evsel,
>  	if (sched->map.comp && new_cpu)
>  		color_fprintf(stdout, color, " (CPU %d)", this_cpu);
>  
> -out:
>  	color_fprintf(stdout, color, "\n");
>  
> +out:
>  	thread__put(sched_in);
>  
>  	return 0;