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Date: Tue, 12 Feb 2019 11:14:10 +0800 From: 禹舟键 <ufo19890607@...il.com> To: Peter Zijlstra <peterz@...radead.org> Cc: mingo@...hat.com, 王贇 <yun.wang@...ux.alibaba.com>, Wind Yu <yuzhoujian@...ichuxing.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] sched/debug: Show intergroup and hierarchy sum wait time of a task group Hi, Peter I think hierarchy wait time for task groups is worth accounting despite with a little extra overhead. Because we can evaluate task groups' condition with a more direct metric. We cannot get the real situation just with some general metrics, like idle or loadavg, since their value is decreased with the elapse of time. So, I think general metrics cannot satisify the request for task groups. Thanks Yuzhoujian Peter Zijlstra <peterz@...radead.org> 于2019年2月7日周四 上午1:19写道: > > On Wed, Jan 23, 2019 at 05:46:56PM +0800, ufo19890607@...il.com wrote: > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index e2ff4b6..35e89ca 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -858,6 +858,19 @@ static void update_curr_fair(struct rq *rq) > > } > > > > static inline void > > +update_hierarchy_wait_sum(struct sched_entity *se, > > + u64 delta_wait) > > +{ > > + for_each_sched_entity(se) { > > + struct cfs_rq *cfs_rq = cfs_rq_of(se); > > + > > + if (cfs_rq->tg != &root_task_group) > > + __schedstat_add(cfs_rq->hierarchy_wait_sum, > > + delta_wait); > > + } > > +} > > + > > +static inline void > > update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) > > { > > struct task_struct *p; > > @@ -880,6 +893,7 @@ static void update_curr_fair(struct rq *rq) > > return; > > } > > trace_sched_stat_wait(p, delta); > > + update_hierarchy_wait_sum(se, delta); > > } > > > > __schedstat_set(se->statistics.wait_max, > > The problem I have with this is that it will make schedstats even more > expensive :/
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