Re: [CFS Bandwidth Control v4 5/7] sched: add exports tracking cfs bandwidth control statistics

[Balbir Singh <balbir@linux.vnet.ibm.com>]

* Paul Turner <pjt@google.com> [2011-02-15 19:18:36]:

> From: Nikhil Rao <ncrao@google.com>
> 
> This change introduces statistics exports for the cpu sub-system, these are
> added through the use of a stat file similar to that exported by other
> subsystems.
> 
> The following exports are included:
> 
> nr_periods:	number of periods in which execution occurred
> nr_throttled:	the number of periods above in which execution was throttle
> throttled_time:	cumulative wall-time that any cpus have been throttled for
> this group
> 
> Signed-off-by: Paul Turner <pjt@google.com>
> Signed-off-by: Nikhil Rao <ncrao@google.com>
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
>  kernel/sched.c      |   26 ++++++++++++++++++++++++++
>  kernel/sched_fair.c |   16 +++++++++++++++-
>  2 files changed, 41 insertions(+), 1 deletion(-)
> 
> Index: tip/kernel/sched.c
> ===================================================================
> --- tip.orig/kernel/sched.c
> +++ tip/kernel/sched.c
> @@ -254,6 +254,11 @@ struct cfs_bandwidth {
>  	ktime_t			period;
>  	u64			runtime, quota;
>  	struct hrtimer		period_timer;
> +
> +	/* throttle statistics */
> +	u64			nr_periods;
> +	u64			nr_throttled;
> +	u64			throttled_time;
>  };
>  #endif
> 
> @@ -389,6 +394,7 @@ struct cfs_rq {
>  #ifdef CONFIG_CFS_BANDWIDTH
>  	u64 quota_assigned, quota_used;
>  	int throttled;
> +	u64 throttled_timestamp;
>  #endif
>  #endif
>  };
> @@ -426,6 +432,10 @@ void init_cfs_bandwidth(struct cfs_bandw
> 
>  	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
>  	cfs_b->period_timer.function = sched_cfs_period_timer;
> +
> +	cfs_b->nr_periods = 0;
> +	cfs_b->nr_throttled = 0;
> +	cfs_b->throttled_time = 0;
>  }
> 
>  static
> @@ -9332,6 +9342,18 @@ static int cpu_cfs_period_write_u64(stru
>  	return tg_set_cfs_period(cgroup_tg(cgrp), cfs_period_us);
>  }
> 
> +static int cpu_stats_show(struct cgroup *cgrp, struct cftype *cft,
> +		struct cgroup_map_cb *cb)
> +{
> +	struct task_group *tg = cgroup_tg(cgrp);
> +	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
> +
> +	cb->fill(cb, "nr_periods", cfs_b->nr_periods);
> +	cb->fill(cb, "nr_throttled", cfs_b->nr_throttled);
> +	cb->fill(cb, "throttled_time", cfs_b->throttled_time);
> +
> +	return 0;
> +}
>  #endif /* CONFIG_CFS_BANDWIDTH */
>  #endif /* CONFIG_FAIR_GROUP_SCHED */
> 
> @@ -9378,6 +9400,10 @@ static struct cftype cpu_files[] = {
>  		.read_u64 = cpu_cfs_period_read_u64,
>  		.write_u64 = cpu_cfs_period_write_u64,
>  	},
> +	{
> +		.name = "stat",
> +		.read_map = cpu_stats_show,
> +	},
>  #endif
>  #ifdef CONFIG_RT_GROUP_SCHED
>  	{
> Index: tip/kernel/sched_fair.c
> ===================================================================
> --- tip.orig/kernel/sched_fair.c
> +++ tip/kernel/sched_fair.c
> @@ -1519,17 +1519,25 @@ static void throttle_cfs_rq(struct cfs_r
> 
>  out_throttled:
>  	cfs_rq->throttled = 1;
> +	cfs_rq->throttled_timestamp = rq_of(cfs_rq)->clock;
>  	update_cfs_rq_load_contribution(cfs_rq, 1);
>  }
> 
>  static void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
>  {
>  	struct rq *rq = rq_of(cfs_rq);
> +	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
>  	struct sched_entity *se;
> 
>  	se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
> 
>  	update_rq_clock(rq);
> +	/* update stats */
> +	raw_spin_lock(&cfs_b->lock);
> +	cfs_b->throttled_time += (rq->clock - cfs_rq->throttled_timestamp);
> +	raw_spin_unlock(&cfs_b->lock);
> +	cfs_rq->throttled_timestamp = 0;
> +
>  	/* (Try to) avoid maintaining share statistics for idle time */
>  	cfs_rq->load_stamp = cfs_rq->load_last = rq->clock_task;
> 
> @@ -1571,7 +1579,7 @@ static void account_cfs_rq_quota(struct 
> 
>  static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
>  {
> -	int i, idle = 1;
> +	int i, idle = 1, num_throttled = 0;
>  	u64 delta;
>  	const struct cpumask *span;
> 
> @@ -1593,6 +1601,7 @@ static int do_sched_cfs_period_timer(str
> 
>  		if (!cfs_rq_throttled(cfs_rq))
>  			continue;
> +		num_throttled++;
> 
>  		delta = tg_request_cfs_quota(cfs_rq->tg);
> 
> @@ -1608,6 +1617,11 @@ static int do_sched_cfs_period_timer(str
>  		}
>  	}
> 
> +	/* update throttled stats */
> +	cfs_b->nr_periods++;
> +	if (num_throttled)
> +		cfs_b->nr_throttled++;
> +
>  	return idle;
>  }
>

Should we consider integrating this in cpuacct, it would be difficult
if we spill over stats between controllers. 

-- 
	Three Cheers,
	Balbir