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: <CAE4VaGDnmVijX5pY-1zdrdgB=EFqwiL8VOWqxGDn6scATb0L0A@mail.gmail.com>
Date:	Fri, 24 Jun 2016 14:35:56 +0200
From:	Jirka Hladky <jhladky@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	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>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Mike Galbraith <umgwanakikbuti@...il.com>, bsegall@...gle.com,
	pjt@...gle.com, matt@...eblueprint.co.uk
Subject: Re: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and
 SPECjvm2008 benchmarks against 4.6 kernel

OK, I have applied to v4.7-rc4 via git am

Compiling kernel, should have the results soon.

Jirka

On Fri, Jun 24, 2016 at 2:09 PM, Jirka Hladky <jhladky@...hat.com> wrote:
> Thank you Peter!
>
> Should I apply it to v4.7-rc4 ?
>
> Jirka
>
> On Fri, Jun 24, 2016 at 2:02 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> On Fri, Jun 24, 2016 at 09:44:41AM +0200, Jirka Hladky wrote:
>>> Hi Peter,
>>>
>>> thanks a lot for looking into it!
>>>
>>> I have tried to disable autogroups
>>>
>>> sysctl -w kernel.sched_autogroup_enabled=0
>>>
>>> and I can confirm that performance is then back at level as in 4.6 kernel.
>>
>> So unless the heat has made me do really silly things, the below seems
>> to cure things. Could you please verify?
>>
>>
>> ---
>>  kernel/sched/fair.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> 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;
>>
>>         return tg_weight;
>>  }
>> @@ -2494,7 +2494,7 @@ static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
>>         long tg_weight, load, shares;
>>
>>         tg_weight = calc_tg_weight(tg, cfs_rq);
>> -       load = cfs_rq->load.weight;
>> +       load = cfs_rq->avg.load_avg;
>>
>>         shares = (tg->shares * load);
>>         if (tg_weight)