linux-kernel - Re: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and SPECjvm2008 benchmarks against 4.6 kernel

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Message-ID: <CAE4VaGCdDyWnL=Kx1eq88N3S+JEBBVSJ3ehGOwvgVQ2ZQiYjhg@mail.gmail.com>
Date:	Sat, 25 Jun 2016 00:13:21 +0200
From:	Jirka Hladky <jhladky@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Vincent Guittot <vincent.guittot@...aro.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Kamil Kolakowski <kkolakow@...hat.com>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Yuyang Du <yuyang.du@...el.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Benjamin Segall <bsegall@...gle.com>,
	Paul Turner <pjt@...gle.com>,
	Matt Fleming <matt@...eblueprint.co.uk>
Subject: Re: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and
 SPECjvm2008 benchmarks against 4.6 kernel

Hi Peter,

I have compiled your version of linux kernel and run the SPECjvm2008
tests. Results are fine, performance is at the level of 4.6 kernel.

$ git rev-parse HEAD
02548776ded1185e6e16ad0a475481e982741ee9

Jirka




On Fri, Jun 24, 2016 at 5:54 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> 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