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    SubjectRe: [CFS Bandwidth Control v4 5/7] sched: add exports tracking cfs bandwidth control statistics
    On Tue, Feb 22, 2011 at 08:44:20AM +0530, Balbir Singh wrote:
    > * 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.

    Given that cpuacct controller can be mounted independently, I am not sure
    if we should integrate these stats. These stats come from cpu controller.

    I initially had similar stats as part of /proc/sched_debug since there
    are a bunch of other group specific stats (including rt throttle stats)
    in /proc/sched_debug.

    Regards,
    Bharata.


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