Messages in this thread | | | Date | Fri, 24 Jun 2016 15:33:47 +0200 | From | Peter Zijlstra <> | Subject | Re: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and SPECjvm2008 benchmarks against 4.6 kernel |
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On Fri, Jun 24, 2016 at 03:23:37PM +0200, Vincent Guittot wrote: > On 24 June 2016 at 15:09, Peter Zijlstra <peterz@infradead.org> wrote: > > On Fri, Jun 24, 2016 at 02:44:07PM +0200, Vincent Guittot wrote: > > > >> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > >> > index 22d64b3f5876..d4f6fb2f3057 100644 > >> > --- a/kernel/sched/fair.c > >> > +++ b/kernel/sched/fair.c > >> > @@ -2484,7 +2484,7 @@ static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq) > >> > */ > >> > tg_weight = atomic_long_read(&tg->load_avg); > >> > tg_weight -= cfs_rq->tg_load_avg_contrib; > >> > - tg_weight += cfs_rq->load.weight; > >> > + tg_weight += cfs_rq->avg.load_avg; > >> > >> IIUC, you are reverting > >> commit fde7d22e01aa (sched/fair: Fix overly small weight for > >> interactive group entities) > > > > Ah!, I hadn't yet done a git-blame on this. Right you are, we should > > have put a comment there. > > > > So the problem here is that since commit: > > > > 2159197d6677 ("sched/core: Enable increased load resolution on 64-bit kernels") > > > > load.weight and avg.load_avg are in different metrics. Which completely > > wrecked things. > > > > The obvious alternative is using: > > > > scale_load_down(cfs_rq->load.weight); > > > > Let me go run that through the benchmark. > > Yes, looks to be good alternative
Does indeed also work. Let me go write a Changelog and try and magic it into sched/urgent.
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