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SubjectRe: [PATCH] sched: fair: fix missed CONFIG_SCHEDSTATS
On Wed, Mar 06, 2019 at 04:43:46PM +0800, Yafang Shao wrote:
> When I'm using trace_sched_stat_{iowait, blocked, wait, sleep} to
> measure how long the processes are stalled, there's always no output from
> trace_pipe while there're really some tasks in uninterruptible sleep
> state. That makes me confused, so I try to investigate why.
> Finally I find the reason is that CONFIG_SCHEDSTATS is not set.
>
> To avoid such kind of confusion, we should not expose these tracepoints
> if CONFIG_SCHEDSTATS is not set.

Yeah, lets not sprinkle #ifdef. Big fat NAK.

Also, the below seem to indicate your compiler is stupid. Without
CONFIG_SCHEDSTAT, schedstat_enabled() should be a constant 0 and DCE
should delete all code.

> @@ -976,6 +982,7 @@ static void update_curr_fair(struct rq *rq)
> static inline void
> update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> {
> +#ifdef CONFIG_SCHEDSTATS
> if (!schedstat_enabled())
> return;
>
> @@ -988,12 +995,13 @@ static void update_curr_fair(struct rq *rq)
>
> if (flags & ENQUEUE_WAKEUP)
> update_stats_enqueue_sleeper(cfs_rq, se);
> +#endif
> }
>
> static inline void
> update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> {
> -
> +#ifdef CONFIG_SCHEDSTATS
> if (!schedstat_enabled())
> return;
>
> @@ -1014,6 +1022,7 @@ static void update_curr_fair(struct rq *rq)
> __schedstat_set(se->statistics.block_start,
> rq_clock(rq_of(cfs_rq)));
> }
> +#endif
> }
>
> /*
> @@ -4090,6 +4099,7 @@ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
> update_stats_curr_start(cfs_rq, se);
> cfs_rq->curr = se;
>
> +#ifdef CONFIG_SCHEDSTATS
> /*
> * Track our maximum slice length, if the CPU's load is at
> * least twice that of our own weight (i.e. dont track it
> @@ -4100,6 +4110,7 @@ static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
> max((u64)schedstat_val(se->statistics.slice_max),
> se->sum_exec_runtime - se->prev_sum_exec_runtime));
> }
> +#endif
>
> se->prev_sum_exec_runtime = se->sum_exec_runtime;
> }
> --
> 1.8.3.1
>

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