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


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