Commit bcb1704a authored by Huaixin Chang's avatar Huaixin Chang Committed by Peter Zijlstra
Browse files

sched/fair: Add cfs bandwidth burst statistics 



Two new statistics are introduced to show the internal of burst feature
and explain why burst helps or not.

nr_bursts:  number of periods bandwidth burst occurs
burst_time: cumulative wall-time (in nanoseconds) that any cpus has
	    used above quota in respective periods

Co-developed-by: default avatarShanpei Chen <shanpeic@linux.alibaba.com>
Signed-off-by: default avatarShanpei Chen <shanpeic@linux.alibaba.com>
Co-developed-by: default avatarTianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: default avatarTianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: default avatarHuaixin Chang <changhuaixin@linux.alibaba.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarDaniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210830032215.16302-2-changhuaixin@linux.alibaba.com
parent 2cae3948

kernel/sched/core.c

+10 −3
Original line number Diff line number Diff line
@@ -10406,6 +10406,9 @@ static int cpu_cfs_stat_show(struct seq_file *sf, void *v) 
		seq_printf(sf, "wait_sum %llu\n", ws);

	}



	seq_printf(sf, "nr_bursts %d\n", cfs_b->nr_burst);

	seq_printf(sf, "burst_time %llu\n", cfs_b->burst_time);



	return 0;

}

#endif /* CONFIG_CFS_BANDWIDTH */
@@ -10521,16 +10524,20 @@ static int cpu_extra_stat_show(struct seq_file *sf, 
	{

		struct task_group *tg = css_tg(css);

		struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;

		u64 throttled_usec;

		u64 throttled_usec, burst_usec;



		throttled_usec = cfs_b->throttled_time;

		do_div(throttled_usec, NSEC_PER_USEC);

		burst_usec = cfs_b->burst_time;

		do_div(burst_usec, NSEC_PER_USEC);



		seq_printf(sf, "nr_periods %d\n"

			   "nr_throttled %d\n"

			   "throttled_usec %llu\n",

			   "throttled_usec %llu\n"

			   "nr_bursts %d\n"

			   "burst_usec %llu\n",

			   cfs_b->nr_periods, cfs_b->nr_throttled,

			   throttled_usec);

			   throttled_usec, cfs_b->nr_burst, burst_usec);

	}

#endif

	return 0;

kernel/sched/fair.c

+9 −0
Original line number Diff line number Diff line
@@ -4715,11 +4715,20 @@ static inline u64 sched_cfs_bandwidth_slice(void) 
 */

void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)

{

	s64 runtime;



	if (unlikely(cfs_b->quota == RUNTIME_INF))

		return;



	cfs_b->runtime += cfs_b->quota;

	runtime = cfs_b->runtime_snap - cfs_b->runtime;

	if (runtime > 0) {

		cfs_b->burst_time += runtime;

		cfs_b->nr_burst++;

	}



	cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst);

	cfs_b->runtime_snap = cfs_b->runtime;

}



static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)

kernel/sched/sched.h

+3 −0
Original line number Diff line number Diff line
@@ -369,6 +369,7 @@ struct cfs_bandwidth { 
	u64			quota;

	u64			runtime;

	u64			burst;

	u64			runtime_snap;

	s64			hierarchical_quota;



	u8			idle;
@@ -381,7 +382,9 @@ struct cfs_bandwidth { 
	/* Statistics: */

	int			nr_periods;

	int			nr_throttled;

	int			nr_burst;

	u64			throttled_time;

	u64			burst_time;

#endif

};