[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <5932bbd6-afe7-416f-b590-c9f5c1c02db5@gmail.com>
Date: Thu, 16 Nov 2023 19:33:30 +0800
From: Yiwei Lin <s921975628@...il.com>
To: Abel Wu <wuyun.abel@...edance.com>, mingo@...hat.com,
peterz@...radead.org
Cc: vincent.guittot@...aro.org, dietmar.eggemann@....com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] sched/fair: Update min_vruntime in more relaxed way
On 11/16/23 19:16, Abel Wu wrote:
> On 11/16/23 6:54 PM, Yiwei Lin Wrote:
>> As EEVDF adopts lag-based solution which is irrespective of
>> min_vruntime like CFS before, min_vruntime is only used as
>> an offset to avoid overflow on evaluation of avg_vruntime now.
>> Rely on the fact we will always update_curr() before change
>> to cfs_rq, it seems to make sense if we just
>> update_min_vruntime() with update_curr() to reduce the cost.
>>
>> Signed-off-by: Yiwei Lin <s921975628@...il.com>
>> ---
>> kernel/sched/fair.c | 20 +-------------------
>> 1 file changed, 1 insertion(+), 19 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 07f555857..5c40adfae 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -3815,17 +3815,8 @@ static void reweight_entity(struct cfs_rq
>> *cfs_rq, struct sched_entity *se,
>> enqueue_load_avg(cfs_rq, se);
>> if (se->on_rq) {
>> update_load_add(&cfs_rq->load, se->load.weight);
>> - if (!curr) {
>> - /*
>> - * The entity's vruntime has been adjusted, so let's check
>> - * whether the rq-wide min_vruntime needs updated too.
>> Since
>> - * the calculations above require stable min_vruntime
>> rather
>> - * than up-to-date one, we do the update at the end of the
>> - * reweight process.
>> - */
>> + if (!curr)
>> __enqueue_entity(cfs_rq, se);
>> - update_min_vruntime(cfs_rq);
>> - }
>> }
>> }
>> @@ -5347,15 +5338,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct
>> sched_entity *se, int flags)
>> update_cfs_group(se);
>> - /*
>> - * Now advance min_vruntime if @se was the entity holding it back,
>> - * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case
>> we'll be
>> - * put back on, and if we advance min_vruntime, we'll be placed
>> back
>> - * further than we started -- ie. we'll be penalized.
>> - */
>> - if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
>> - update_min_vruntime(cfs_rq);
>> -
>> if (cfs_rq->nr_running == 0)
>> update_idle_cfs_rq_clock_pelt(cfs_rq);
>> }
>
> For now, core pick of core scheduling relies on min_vruntime to be fresh,
> so please just fix commit eab03c23c2a1 to preserve its original behavior
> by moving update_min_vruntime() to proper position. And behavior change
> can be posted separated.
Sorry for not noticing the requirement on core scheduling and applying
bad solution. I should take a closer look for the influence when
changing the approach to update_min_vruntime().
I'll send another patch which just move update_min_vruntime() to the
right place later on.
>
> BTW it seems unnecessary to include a cover-letter for a single patch.
>
Got it! Still learning how to work with the kernel mailing list. Thanks
for the kind suggestion!
> Thanks,
> Abel
Powered by blists - more mailing lists