Re: [RFC/PATCH] perf sched: Implement 'perf sched runtime' command

[David Ahern <dsahern@gmail.com>]

On 8/24/15 11:11 PM, Namhyung Kim wrote:
>
> +static int perf_sched__read_runtime_events(struct perf_sched *sched)
> +{
> +	const struct perf_evsel_str_handler handlers[] = {
> +		{ "sched:sched_switch",	      process_sched_switch_event, },
> +		{ "sched:sched_stat_runtime", process_sched_runtime_event, },
> +		{ "sched:sched_stat_sleep",   process_sched_sleep_event, },
> +		{ "sched:sched_stat_wait",    process_sched_wait_event, },
> +		{ "sched:sched_stat_iowait",  process_sched_iowait_event, },
> +		{ "sched:sched_migrate_task", process_sched_migrate_task_event, },
> +	};

I like the concept (obviously since I have invested so much time in 
other solutions). But... you cannot rely on the sched_stat tracepoints 
being enabled. I believe it is a performance hit to have 
CONFIG_SCHEDSTATS enabled and distributions (e.g., Fedora) do not have 
it enabled.