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    Subject[PATCH v3 5/7] sched: add exports tracking cfs bandwidth control statistics
    sched: add exports tracking cfs bandwidth control statistics

    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: Bharata B Rao <bharata@linux.vnet.ibm.com>
    ---
    kernel/sched.c | 26 ++++++++++++++++++++++++++
    kernel/sched_fair.c | 18 +++++++++++++++++-
    2 files changed, 43 insertions(+), 1 deletion(-)

    --- a/kernel/sched.c
    +++ b/kernel/sched.c
    @@ -252,6 +252,11 @@ 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

    @@ -388,6 +393,7 @@ struct cfs_rq {
    #ifdef CONFIG_CFS_BANDWIDTH
    u64 quota_assigned, quota_used;
    int throttled;
    + u64 throttled_timestamp;
    #endif
    #endif
    };
    @@ -425,6 +431,10 @@ 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
    @@ -9029,6 +9039,18 @@ 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 */

    @@ -9075,6 +9097,10 @@ 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
    {
    --- a/kernel/sched_fair.c
    +++ b/kernel/sched_fair.c
    @@ -1224,16 +1224,26 @@ static void throttle_cfs_rq(struct cfs_r

    out_throttled:
    cfs_rq->throttled = 1;
    + cfs_rq->throttled_timestamp = rq_of(cfs_rq)->clock;
    }

    static void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
    {
    struct sched_entity *se;
    struct rq *rq = rq_of(cfs_rq);
    + struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

    se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];

    + /* update stats */
    + update_rq_clock(rq);
    + 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 = 0;
    + cfs_rq->throttled_timestamp = 0;
    +
    for_each_sched_entity(se) {
    if (se->on_rq)
    break;
    @@ -1271,7 +1281,7 @@ 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;

    @@ -1293,6 +1303,7 @@ 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);

    @@ -1306,6 +1317,11 @@ static int do_sched_cfs_period_timer(str
    }
    }

    + /* update throttled stats */
    + cfs_b->nr_periods++;
    + if (num_throttled)
    + cfs_b->nr_throttled++;
    +
    return idle;
    }


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