Re: [PATCH 3/3] perf tools: Clarify the output of perf sched map.

[Ingo Molnar <mingo@kernel.org>]

* Dongsheng Yang <yangds.fnst@cn.fujitsu.com> wrote:

> From: Dongsheng <yangds.fnst@cn.fujitsu.com>
> 
> In output of perf sched map, any shortname of thread will be explained
> at the first time when it appear.
> 
> Example:
> 	      *A0       228836.978985 secs A0 => perf:23032
>           *.   A0       228836.979016 secs B0 => swapper:0
>            .  *C0       228836.979099 secs C0 => migration/3:22
>   *A0      .   C0       228836.979115 secs
>    A0      .  *.        228836.979115 secs
> 
> But B0, which is explained as swapper:0 did not appear in the
> left part of output. Instead, we use '.' as the shortname of
> swapper:0. So the comment of "B0 => swapper:0" is not easy to
> understand.
> 
> This patch clarify the output of perf sched map with not allocating
> one letter-number shortname for swapper:0 and print ". => swapper:0"
> as the explaination for swapper:0.
> 
> Example:
>               *A0       228836.978985 secs A0 => perf:23032
>           * .  A0       228836.979016 secs . => swapper:0
>             . *B0       228836.979099 secs B0 => migration/3:22
>   *A0       .  B0       228836.979115 secs
>    A0       . * .       228836.979115 secs
>    A0     *C0   .       228836.979225 secs C0 => ksoftirqd/2:18
>    A0     *D0   .       228836.979236 secs D0 => rcu_sched:7

Sounds good!

I only have some minor nits about the code:

>  tools/perf/builtin-sched.c | 35 +++++++++++++++++++----------------
>  1 file changed, 19 insertions(+), 16 deletions(-)
> 
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index 4f0dd21..c2bf8f2 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -1300,17 +1300,23 @@ static int map_switch_event(struct perf_sched *sched, struct perf_evsel *evsel,
>  
>  	new_shortname = 0;
>  	if (!sched_in->shortname[0]) {
> -		sched_in->shortname[0] = sched->next_shortname1;
> -		sched_in->shortname[1] = sched->next_shortname2;
> -
> -		if (sched->next_shortname1 < 'Z') {
> -			sched->next_shortname1++;
> -		} else {
> -			sched->next_shortname1='A';
> -			if (sched->next_shortname2 < '9') {
> -				sched->next_shortname2++;
> +		if (!strcmp(thread__comm_str(sched_in), "swapper")) {
> +			sched_in->shortname[0] = '.';
> +			sched_in->shortname[1] = '\0';
> +		}
> +		else {

Should be '} else {' as per kernel coding style.

Also, a comment about handling the idle task in a special way would be 
useful - for the far future when this discussion will be distant 
memories or less!

With those nits addressed:

Acked-by: Ingo Molnar <mingo@kernel.org>

Thanks,

	Ingo