Messages in this thread | | | Date | Tue, 25 Jun 2013 21:13:15 +0800 | From | Alex Shi <> | Subject | Re: [Resend patch v8 0/13] use runnable load in schedule balance |
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On 06/24/2013 11:37 PM, Alex Shi wrote: > On 06/24/2013 06:40 PM, Paul Turner wrote: >>>> Ingo & Peter, >>>> >>>> This patchset was discussed spread and deeply. >>>> >>>> Now just 6th/8th patch has some arguments on them, Paul think it is >>>> better to consider blocked_load_avg in balance, since it is helpful on >>>> some scenarios, but I think on most of scenarios, the blocked_load_avg >>>> just cause load imbalance among cpus. and plus testing show with >>>> blocked_load_avg the performance is just worse on some benchmarks. So, I >>>> still prefer to keep it out of balance. >> I think you have perhaps misunderstood what I was trying to explain. >> >> I have no problems with not including blocked load in load-balance, in >> fact, I encouraged not accumulating it in an average of averages in >> CPU load. >> > > Many thanks for re-clarification! >> The problem is that your current approach has removed it both from >> load-balance _and_ from shares distribution; isolation matters as much >> as performance in the cgroup case (otherwise you would just not use >> cgroups). I would expect the latter to have quite negative effects on >> fairness, this is my primary concern. >> > > So the argument is just on patch 'sched/tg: remove blocked_load_avg in balance'. :) > > I understand your correctness concern. but blocked_load_avg still will be decayed to zero in few hundreds ms. So such correctness needs just in few hundreds ms. (and cause performance drop) > The blocked_load_avg is decayed on same degree as runnable load, it is a bit overweight since task slept. since it may will be waken up on other cpu. So to relieve this overweight, could we use the half or a quarter weight of blocked_load_avg? like following: >
Ping to Paul!
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index ddbc19f..395f57c 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -1358,7 +1358,7 @@ static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq, > struct task_group *tg = cfs_rq->tg; > s64 tg_contrib; > > - tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg; > + tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg / 2; > tg_contrib -= cfs_rq->tg_load_contrib; > > if (force_update || abs64(tg_contrib) > cfs_rq->tg_load_contrib / 8) { > >>>> >>>> http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg455196.html >>>> >>>> Is it the time to do the decision or give more comments? Thanks! > >
-- Thanks Alex
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