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SubjectRe: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and SPECjvm2008 benchmarks against 4.6 kernel
Thank you Peter!

Should I apply it to v4.7-rc4 ?

Jirka

On Fri, Jun 24, 2016 at 2:02 PM, Peter Zijlstra <peterz@infradead.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)

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