On Fri, Oct 10, 2014 at 10:21:56AM +0800, Yuyang Du wrote:
> +/* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
> +static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
> {
> + int decayed;
>
> + if (atomic_long_read(&cfs_rq->removed_load_avg)) {
> + long r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
> + cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - r, 0);
> + cfs_rq->avg.load_sum =
> + max_t(s64, cfs_rq->avg.load_sum - r * LOAD_AVG_MAX, 0);
> }
>
> + decayed = __update_load_avg(now, &cfs_rq->avg, cfs_rq->load.weight);
>
> +#ifndef CONFIG_64BIT
> + smp_wmb();
> + cfs_rq->load_last_update_time_copy = cfs_rq->avg.last_update_time;
> +#endif
>
> -static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
> + return decayed;
> +}
> +void remove_entity_load_avg(struct sched_entity *se)
> {
> + struct cfs_rq *cfs_rq = cfs_rq_of(se);
> + u64 last_update_time;
> +
> +#ifndef CONFIG_64BIT
> + u64 last_update_time_copy;
> +
> + do {
> + last_update_time_copy = cfs_rq->load_last_update_time_copy;
> + smp_rmb();
> + last_update_time = cfs_rq->avg.last_update_time;
> + } while (last_update_time != last_update_time_copy);
> +#else
> + last_update_time = cfs_rq->avg.last_update_time;
> +#endif
>
> + __update_load_avg(last_update_time, &se->avg, 0);
> + atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
> }
> +static void migrate_task_rq_fair(struct task_struct *p, int next_cpu)
> {
> /*
> + * We are supposed to update the task to "current" time, then its up to
> date
> + * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
> + * what current time is, so simply throw away the out-of-date time. This
> + * will result in the wakee task is less decayed, but giving the wakee
> more
> + * load sounds not bad.
> */
> + remove_entity_load_avg(&p->se);
> +
> + /* Tell new CPU we are migrated */
> + p->se.avg.last_update_time = 0;
>
> /* We have migrated, no longer consider this task hot */
> + p->se.exec_start = 0;
> }
Because of:
entity_tick()
update_load_avg()
update_cfs_rq_load_avg()
we're likely to only lag TICK_NSEC behind, right? And thus the
truncation we do in migrate_task_rq_fair() is of equal size.
Hmm,. one problem, cgroup cfs_rq can be idle for a long while and not
get get any ticks at all, so those can lag unbounded. Then again, this
appears to be a problem in the current code too, hmm..
Anybody?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
