From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>,
Luca Abeni <luca.abeni@santannapisa.it>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Valentin Schneider <Valentin.Schneider@arm.com>,
Qais Yousef <Qais.Yousef@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/5] sched/deadline: Use __sub_running_bw() throughout dl_change_utilization()
Date: Mon, 29 Jul 2019 18:21:55 +0100 [thread overview]
Message-ID: <fc48cf4a-6153-5ead-72cd-76df4b10d6a0@arm.com> (raw)
In-Reply-To: <20190729164755.GM31398@hirez.programming.kicks-ass.net>
On 7/29/19 5:47 PM, Peter Zijlstra wrote:
> On Fri, Jul 26, 2019 at 09:27:54AM +0100, Dietmar Eggemann wrote:
>> dl_change_utilization() has a BUG_ON() to check that no schedutil
>> kthread (sugov) is entering this function. So instead of calling
>> sub_running_bw() which checks for the special entity related to a
>> sugov thread, call the underlying function __sub_running_bw().
>>
>> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
>> ---
>> kernel/sched/deadline.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>> index 99d4c24a8637..1fa005f79307 100644
>> --- a/kernel/sched/deadline.c
>> +++ b/kernel/sched/deadline.c
>> @@ -164,7 +164,7 @@ void dl_change_utilization(struct task_struct *p, u64 new_bw)
>>
>> rq = task_rq(p);
>> if (p->dl.dl_non_contending) {
>> - sub_running_bw(&p->dl, &rq->dl);
>> + __sub_running_bw(p->dl.dl_bw, &rq->dl);
>> p->dl.dl_non_contending = 0;
>> /*
>> * If the timer handler is currently running and the
>
> I'm confused; the only called of dl_change_utilization() is
> sched_dl_overflow(), and that already checks FLAG_SUGOV and exits before
> calling.
That's right. There is even a BUG_ON(p->dl.flags & SCHED_FLAG_SUGOV) at
the beginning of dl_change_utilization().
> So how can this matter?
We save the 'if (!dl_entity_is_special(dl_se))' from sub_running_bw()
when we call __sub_running_bw() since we know it can't be a special task.
Later in dl_change_utilization() we already use the inner bw accounting
functions __sub_rq_bw() and __add_rq_bw().
next prev parent reply other threads:[~2019-07-29 17:22 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-26 8:27 [PATCH 0/5] sched/deadline: Fix double accounting in push_dl_task() & some cleanups Dietmar Eggemann
2019-07-26 8:27 ` [PATCH 1/5] sched/deadline: Fix double accounting of rq/running bw in push_dl_task() Dietmar Eggemann
2019-07-26 10:11 ` luca abeni
2019-07-29 8:59 ` Dietmar Eggemann
2019-07-29 16:10 ` Peter Zijlstra
2019-07-26 13:30 ` luca abeni
2019-07-29 9:00 ` Dietmar Eggemann
2019-07-31 10:32 ` Dietmar Eggemann
2019-07-26 8:27 ` [PATCH 2/5] sched/deadline: Remove unused int flags from __dequeue_task_dl() Dietmar Eggemann
2019-07-29 16:35 ` Peter Zijlstra
2019-07-29 17:12 ` Dietmar Eggemann
2019-07-26 8:27 ` [PATCH 3/5] sched/deadline: Use __sub_running_bw() throughout dl_change_utilization() Dietmar Eggemann
2019-07-29 16:47 ` Peter Zijlstra
2019-07-29 17:21 ` Dietmar Eggemann [this message]
2019-07-26 8:27 ` [PATCH 4/5] sched/deadline: Cleanup on_dl_rq() handling Dietmar Eggemann
2019-07-26 8:37 ` Valentin Schneider
2019-07-26 8:58 ` Qais Yousef
2019-07-26 9:20 ` Juri Lelli
2019-07-26 9:32 ` Valentin Schneider
2019-07-29 16:49 ` Peter Zijlstra
2019-07-30 6:41 ` Juri Lelli
2019-07-30 8:21 ` Peter Zijlstra
2019-07-31 17:32 ` Dietmar Eggemann
2019-07-31 20:20 ` luca abeni
2019-08-01 16:01 ` Dietmar Eggemann
2019-07-26 8:27 ` [PATCH 5/5] sched/deadline: Use return value of SCHED_WARN_ON() in bw accounting Dietmar Eggemann
2019-07-26 10:18 ` luca abeni
2019-07-29 16:54 ` Peter Zijlstra
2019-07-29 16:59 ` Dietmar Eggemann
2019-07-30 8:23 ` Peter Zijlstra
2019-07-30 16:08 ` Dietmar Eggemann
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