Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 20 Jun 2013 09:43:45 +0800 | Subject | Re: [patch v8 4/9] sched: fix slept time double counting in enqueue entity | From | Lei Wen <> |
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Hi Alex,
On Mon, Jun 17, 2013 at 11:41 PM, Alex Shi <alex.shi@intel.com> wrote: > On 06/17/2013 07:51 PM, Paul Turner wrote: >> Can you add something like: >> >> + /* >> + * Task re-woke on same cpu (or else >> migrate_task_rq_fair() >> + * would have made count negative); we must be careful >> to avoid >> + * double-accounting blocked time after synchronizing >> decays. >> + */ >> >> >> Reviewed-by: Paul Turner <pjt@google.com> > > thanks for review! > --- > > From 24d9b43e7a269e6ffee5b874d39812b83812a809 Mon Sep 17 00:00:00 2001 > From: Alex Shi <alex.shi@intel.com> > Date: Thu, 9 May 2013 10:54:13 +0800 > Subject: [PATCH] sched: fix slept time double counting in enqueue entity > > The wakeuped migrated task will __synchronize_entity_decay(se); in > migrate_task_fair, then it needs to set
Should be migrate_task_rq_fair, right? :)
> `se->avg.last_runnable_update -= (-se->avg.decay_count) << 20' > before update_entity_load_avg, in order to avoid slept time is updated > twice for se.avg.load_avg_contrib in both __syncchronize and > update_entity_load_avg. > > but if the slept task is waked up from self cpu, it miss the > last_runnable_update before update_entity_load_avg(se, 0, 1), then the > slept time was used twice in both functions. > So we need to remove the double slept time counting. > > Signed-off-by: Alex Shi <alex.shi@intel.com> > Reviewed-by: Paul Turner <pjt@google.com> > --- > kernel/sched/fair.c | 8 +++++++- > 1 files changed, 7 insertions(+), 1 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index df5b8a9..1e5a5e6 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -1571,7 +1571,13 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, > } > wakeup = 0; > } else { > - __synchronize_entity_decay(se); > + /* > + * Task re-woke on same cpu (or else migrate_task_rq_fair() > + * would have made count negative); we must be careful to avoid > + * double-accounting blocked time after synchronizing decays. > + */ > + se->avg.last_runnable_update += __synchronize_entity_decay(se) > + << 20;
I'm kind of getting confused at here, since migrate_task_rq_fair use below equation to avoid sleep time be accounted for twice. `se->avg.last_runnable_update -= (-se->avg.decay_count) << 20'
Why here we need to use "+=", which the reversed version comparing with previous?
Thanks, Lei
> } > > /* migrated tasks did not contribute to our blocked load */ > -- > 1.7.5.4 > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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