Re: [RFC PATCH 14/14] sched: implement usage tracking

[Paul Turner]

On Tue, Mar 13, 2012 at 9:57 AM, Vincent Guittot
<vincent.guittot@xxxxxxxxxx> wrote:
> Hi Paul,
>
> On 2 February 2012 02:38, Paul Turner <pjt@xxxxxxxxxx> wrote:
>> With the frame-work for runnable tracking now fully in place.  Per-entity usage
>> tracking is a simple and low-overhead addition.
>>
>> Signed-off-by: Paul Turner <pjt@xxxxxxxxxx>
>> Signed-off-by: Ben Segall <bsegall@xxxxxxxxxx>
>> ---
>>  include/linux/sched.h |    1 +
>>  kernel/sched/debug.c  |    3 +++
>>  kernel/sched/fair.c   |   29 +++++++++++++++++++++++------
>>  kernel/sched/sched.h  |    4 ++--
>>  4 files changed, 29 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>> index 09b8c45..209185f 100644
>> --- a/include/linux/sched.h
>> +++ b/include/linux/sched.h
>> @@ -1159,6 +1159,7 @@ struct load_weight {
>>  struct sched_avg {
>>        u64 runnable_avg_sum, runnable_avg_period;
>>        u64 last_runnable_update, decay_count;
>> +       u32 usage_avg_sum;
>
> Why usage_avg_sum is 32bits whereas runnable_avg_sum and
> runnable_avg_period are 64bits long ? You are doing the same
> computation on these 3 variables. Only the computation need to be done
> in 64bits but the result could be saved in 32bits ?

Yes, these fit in 32 bits.

Sorry I have not had a chance to post v2 yet, I've been buried with
unrelated work related to context-switching and LinSched[*].  Now that
those monkeys are wrestled to the ground I'll get this moving again.

[*] LinSched on v3.3-rc7 is now up at:
http://git.kernel.org/?p=linux/kernel/git/pjt/linsched.git;a=shortlog;h=refs/heads/linsched-v3.3-alpha
I'll be sending an announcement email in a few hours.

>
> Regards,
> Vincent
>
>>        unsigned long load_avg_contrib;
>>
>>        int contributes_blocked_load;
>> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
>> index 0911ec6..4d39069 100644
>> --- a/kernel/sched/debug.c
>> +++ b/kernel/sched/debug.c
>> @@ -93,6 +93,7 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
>>        P(se->load.weight);
>>        P(se->avg.runnable_avg_sum);
>>        P(se->avg.runnable_avg_period);
>> +       P(se->avg.usage_avg_sum);
>>        P(se->avg.load_avg_contrib);
>>        P(se->avg.decay_count);
>>  #undef PN
>> @@ -228,6 +229,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
>>                        cfs_rq->tg_runnable_contrib);
>>        SEQ_printf(m, "  .%-30s: %d\n", "tg->runnable_avg",
>>                        atomic_read(&cfs_rq->tg->runnable_avg));
>> +       SEQ_printf(m, "  .%-30s: %d\n", "tg->usage_avg",
>> +                       atomic_read(&cfs_rq->tg->usage_avg));
>>  #endif
>>
>>        print_cfs_group_stats(m, cpu, cfs_rq->tg);
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index ad524bb..222c2c9 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -997,7 +997,8 @@ static u32 __compute_runnable_contrib(int n)
>>  */
>>  static __always_inline int __update_entity_runnable_avg(u64 now,
>>                                                        struct sched_avg *sa,
>> -                                                       int runnable)
>> +                                                       int runnable,
>> +                                                       int running)
>>  {
>>        u64 delta;
>>        u32 periods, runnable_contrib;
>> @@ -1026,6 +1027,8 @@ static __always_inline int __update_entity_runnable_avg(u64 now,
>>                delta_w = 1024 - delta_w;
>>                if (runnable)
>>                        sa->runnable_avg_sum += delta_w;
>> +               if (running)
>> +                       sa->usage_avg_sum += delta_w;
>>                sa->runnable_avg_period += delta_w;
>>
>>                delta -= delta_w;
>> @@ -1036,15 +1039,20 @@ static __always_inline int __update_entity_runnable_avg(u64 now,
>>                                                  periods + 1);
>>                sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
>>                                                  periods + 1);
>> +               sa->usage_avg_sum = decay_load(sa->usage_avg_sum, periods + 1);
>>
>>                runnable_contrib = __compute_runnable_contrib(periods);
>>                if (runnable)
>>                        sa->runnable_avg_sum += runnable_contrib;
>> +               if (running)
>> +                       sa->usage_avg_sum += runnable_contrib;
>>                sa->runnable_avg_period += runnable_contrib;
>>        }
>>
>>        if (runnable)
>>                sa->runnable_avg_sum += delta;
>> +       if (running)
>> +               sa->usage_avg_sum += delta;
>>        sa->runnable_avg_period += delta;
>>
>>        return decayed;
>> @@ -1081,14 +1089,21 @@ static inline void __update_tg_runnable_avg(struct sched_avg *sa,
>>                                                  struct cfs_rq *cfs_rq)
>>  {
>>        struct task_group *tg = cfs_rq->tg;
>> -       long contrib;
>> +       long contrib, usage_contrib;
>>
>>        contrib = (sa->runnable_avg_sum << 12) / (sa->runnable_avg_period + 1);
>>        contrib -= cfs_rq->tg_runnable_contrib;
>>
>> -       if (abs(contrib) > cfs_rq->tg_runnable_contrib/64) {
>> +       usage_contrib = (sa->usage_avg_sum << 12) / (sa->runnable_avg_period + 1);
>> +       usage_contrib -= cfs_rq->tg_usage_contrib;
>> +
>> +       if ((abs(contrib) > cfs_rq->tg_runnable_contrib/64) ||
>> +           (abs(usage_contrib) > cfs_rq->tg_usage_contrib/64)) {
>>                atomic_add(contrib, &tg->runnable_avg);
>>                cfs_rq->tg_runnable_contrib += contrib;
>> +
>> +               atomic_add(usage_contrib, &tg->usage_avg);
>> +               cfs_rq->tg_usage_contrib += usage_contrib;
>>        }
>>  }
>>
>> @@ -1164,8 +1179,8 @@ static inline void update_entity_load_avg(struct sched_entity *se,
>>        struct cfs_rq *cfs_rq = cfs_rq_of(se);
>>        long contrib_delta;
>>
>> -       if(!__update_entity_runnable_avg(rq_of(cfs_rq)->clock_task, &se->avg,
>> -                                       se->on_rq))
>> +       if(!__update_entity_runnable_avg(cfs_rq_clock_task(cfs_rq), &se->avg,
>> +                                        se->on_rq, cfs_rq->curr == se))
>>                return;
>>
>>        contrib_delta = __update_entity_load_avg_contrib(se);
>> @@ -1210,7 +1225,8 @@ static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
>>
>>  static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
>>  {
>> -       __update_entity_runnable_avg(rq->clock_task, &rq->avg, runnable);
>> +       __update_entity_runnable_avg(rq->clock_task, &rq->avg, runnable,
>> +                                    runnable);
>>        __update_tg_runnable_avg(&rq->avg, &rq->cfs);
>>  }
>>
>> @@ -1590,6 +1606,7 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
>>                 */
>>                update_stats_wait_end(cfs_rq, se);
>>                __dequeue_entity(cfs_rq, se);
>> +               update_entity_load_avg(se, 1);
>>        }
>>
>>        update_stats_curr_start(cfs_rq, se);
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index 77f3297..9602a47 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -117,7 +117,7 @@ struct task_group {
>>
>>        atomic_t load_weight;
>>        atomic64_t load_avg;
>> -       atomic_t runnable_avg;
>> +       atomic_t runnable_avg, usage_avg;
>>  #endif
>>
>>  #ifdef CONFIG_RT_GROUP_SCHED
>> @@ -260,7 +260,7 @@ struct cfs_rq {
>>         */
>>        unsigned long h_load;
>>
>> -       u32 tg_runnable_contrib;
>> +       u32 tg_runnable_contrib, tg_usage_contrib;
>>        u64 runnable_load_avg, blocked_load_avg;
>>        u64 tg_load_contrib;
>>        atomic64_t decay_counter, removed_load;
>>
>>
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