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Date: Fri, 24 Jun 2016 17:54:34 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Jirka Hladky <jhladky@redhat.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>, Kamil Kolakowski <kkolakow@redhat.com>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Yuyang Du <yuyang.du@intel.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Mike Galbraith <umgwanakikbuti@gmail.com>,
        Benjamin Segall <bsegall@google.com>, Paul Turner <pjt@google.com>,
        Matt Fleming <matt@codeblueprint.co.uk>
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 03:42:26PM +0200, Peter Zijlstra wrote:
> On Fri, Jun 24, 2016 at 02:44:07PM +0200, Vincent Guittot wrote:
> > > --- 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)
> 
> Hurm.. looking at that commit again, that seems to wreck
> effective_load(), since that doesn't compensate.
> 
> Maybe I'll remove calc_tg_weight and open code its slightly different
> usages in the two sites.

OK, sorry for not actually posting, but I need to run. Please find the
two patches in:

  git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/urgent