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From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Quentin Perret <qperret@google.com>,
	Vincent Guittot <vincent.guittot@linaro.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Luca Abeni <luca.abeni@santannapisa.it>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Wei Wang <wvw@google.com>, Alessio Balsini <balsini@google.com>,
	Pavan Kondeti <pkondeti@codeaurora.org>,
	Patrick Bellasi <patrick.bellasi@matbug.net>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Qais Yousef <qais.yousef@arm.com>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] sched/topology: Store root domain CPU capacity sum
Date: Tue, 14 Apr 2020 17:27:21 +0200	[thread overview]
Message-ID: <7adf893b-769d-ffa4-71da-d9a93646a88c@arm.com> (raw)
In-Reply-To: <20200414124503.GA236568@google.com>

On 14.04.20 14:45, Quentin Perret wrote:
> On Wednesday 08 Apr 2020 at 19:03:57 (+0200), Vincent Guittot wrote:
>> Or we can do the opposite and only use capacity_orig_of()/rq->cpu_capacity_orig.
>>
>> Is there a case where the max cpu capacity changes over time ? So I
>> would prefer to use cpu_capacity_orig which is a field of scheduler
>> instead of always calling an external arch specific function
> 
> Note however that using arch_scale_cpu_capacity() would be more
> efficient, especially on non-arm/arm64 systems where it is a
> compile-time constant.

or essentially all ARCHs not defining it.

> 
> It's probably a matter of personal taste, but I find rq->cpu_capacity_orig
> superfluous. It wastes space without actually giving you anything no?
> Anybody remembers why it was introduced in the first place?

v3.18 arm providing arch_scale_cpu_capacity()
v4.1  introduction of rq->cpu_capacity_orig
v4.10 arm64 providing arch_scale_cpu_capacity()
...

So it's down to the question of 'minimizing the scheduler calls to an
external arch function' vs 'efficiency'.

  reply	other threads:[~2020-04-14 15:28 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-08  9:50 [PATCH 0/4] Capacity awareness for SCHED_DEADLINE Dietmar Eggemann
2020-04-08  9:50 ` [PATCH 1/4] sched/topology: Store root domain CPU capacity sum Dietmar Eggemann
2020-04-08 12:29   ` Vincent Guittot
2020-04-08 16:30     ` Dietmar Eggemann
2020-04-08 17:03       ` Vincent Guittot
2020-04-09 13:50         ` Dietmar Eggemann
2020-04-09 14:13           ` Vincent Guittot
2020-04-14  9:20             ` Dietmar Eggemann
2020-04-14 12:45         ` Quentin Perret
2020-04-14 15:27           ` Dietmar Eggemann [this message]
2020-04-14 15:43             ` Vincent Guittot
2020-04-08  9:50 ` [PATCH 2/4] sched/deadline: Improve admission control for asymmetric CPU capacities Dietmar Eggemann
2020-04-08 10:42   ` Valentin Schneider
2020-04-08 12:26     ` Dietmar Eggemann
2020-04-08 13:30     ` luca abeni
2020-04-08 14:23       ` Qais Yousef
2020-04-08 15:01       ` Valentin Schneider
2020-04-09 17:29         ` Dietmar Eggemann
2020-04-14 11:40           ` Qais Yousef
2020-04-14 14:29             ` Valentin Schneider
2020-04-14 15:41               ` Qais Yousef
2020-04-14 14:28           ` Valentin Schneider
2020-04-17 12:19           ` Juri Lelli
2020-04-17 14:55             ` Dietmar Eggemann
2020-04-17 15:08               ` Juri Lelli
2020-04-17 15:47                 ` Juri Lelli
2020-04-08  9:50 ` [PATCH 3/4] sched/deadline: Make DL capacity-aware Dietmar Eggemann
2020-04-10 12:52   ` Juri Lelli
2020-04-15  9:39     ` Dietmar Eggemann
2020-04-15 13:20       ` Juri Lelli
2020-04-15 16:42         ` luca abeni
2020-04-16 13:19           ` Juri Lelli
2020-04-08  9:50 ` [PATCH 4/4] sched/deadline: Implement fallback mechanism for !fit case Dietmar Eggemann
2020-04-09 10:25   ` Qais Yousef
2020-04-09 13:00     ` luca abeni
2020-04-09 14:55       ` Qais Yousef
2020-04-09 18:43         ` Dietmar Eggemann
2020-04-14 11:29           ` Qais Yousef

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