Messages in this thread Patch in this message | | | Date | Thu, 19 Oct 2017 17:04:42 +0200 | From | Vincent Guittot <> | Subject | Re: [PATCH -v2 12/18] sched/fair: Rewrite PELT migration propagation |
| |
Subject: [PATCH v2] sched: Update runnable propagation rule
Unlike running, the runnable part can't be directly propagated through the hierarchy when we migrate a task. The main reason is that runnable time can be shared with other sched_entities that stay on the rq and this runnable time will also remain on prev cfs_rq and must not be removed. Instead, we can estimate what should be the new runnable of the prev cfs_rq and check that this estimation stay in a possible range. The prop_runnable_sum is a good estimation when adding runnable_sum but fails most often when we remove it. Instead, we could use the formula below instead:
gcfs_rq's runnable_sum = gcfs_rq->avg.load_sum / gcfs_rq->load.weight (1)
(1) assumes that tasks are equally runnable which is not true but easy to compute.
Beside these estimates, we have several simple rules that help us to filter out wrong ones: -ge->avg.runnable_sum <= than LOAD_AVG_MAX -ge->avg.runnable_sum >= ge->avg.running_sum (ge->avg.util_sum << LOAD_AVG_MAX) -ge->avg.runnable_sum can't increase when we detach a task
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> ---
v2: - Fixed some type mismatch warnings
kernel/sched/fair.c | 46 +++++++++++++++++++++++++++++++++++----------- 1 file changed, 35 insertions(+), 11 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 56f343b..aea89df 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3489,33 +3489,57 @@ update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq static inline void update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq) { - long runnable_sum = gcfs_rq->prop_runnable_sum; - long runnable_load_avg, load_avg; - s64 runnable_load_sum, load_sum; + long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum; + unsigned long runnable_load_avg, load_avg; + s64 delta_sum; + u64 runnable_load_sum, load_sum = 0; if (!runnable_sum) return; gcfs_rq->prop_runnable_sum = 0; + if (runnable_sum >= 0) { + /* Get a rough estimate of the new gcfs_rq's runnable */ + runnable_sum += se->avg.load_sum; + /* ge->avg.runnable_sum can't be higher than LOAD_AVG_MAX */ + runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX); + } else { + /* Get a rough estimate of the new gcfs_rq's runnable */ + if (scale_load_down(gcfs_rq->load.weight)) + load_sum = div_s64(gcfs_rq->avg.load_sum, + scale_load_down(gcfs_rq->load.weight)); + + /* ge->avg.runnable_sum can't increase when removing runnable */ + runnable_sum = min(se->avg.load_sum, load_sum); + } + + /* runnable_sum can't be lower than running_sum */ + running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT; + runnable_sum = max(runnable_sum, running_sum); + load_sum = (s64)se_weight(se) * runnable_sum; load_avg = div_s64(load_sum, LOAD_AVG_MAX); - add_positive(&se->avg.load_sum, runnable_sum); - add_positive(&se->avg.load_avg, load_avg); + delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum; + delta_avg = load_avg - se->avg.load_avg; - add_positive(&cfs_rq->avg.load_avg, load_avg); - add_positive(&cfs_rq->avg.load_sum, load_sum); + se->avg.load_sum = runnable_sum; + se->avg.load_avg = load_avg; + add_positive(&cfs_rq->avg.load_avg, delta_avg); + add_positive(&cfs_rq->avg.load_sum, delta_sum); runnable_load_sum = (s64)se_runnable(se) * runnable_sum; runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX); + delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum; + delta_avg = runnable_load_avg - se->avg.runnable_load_avg; - add_positive(&se->avg.runnable_load_sum, runnable_sum); - add_positive(&se->avg.runnable_load_avg, runnable_load_avg); + se->avg.runnable_load_sum = runnable_sum; + se->avg.runnable_load_avg = runnable_load_avg; if (se->on_rq) { - add_positive(&cfs_rq->avg.runnable_load_avg, runnable_load_avg); - add_positive(&cfs_rq->avg.runnable_load_sum, runnable_load_sum); + add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg); + add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum); } } -- 2.7.4
| |