linux-kernel - Re: [PATCH 3/5] sched/fair: rework load

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Message-ID: <58f79135-4b6c-2507-3f5d-e3c7704bf8b3@arm.com>
Date:   Mon, 29 Jul 2019 15:28:45 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH 3/5] sched/fair: rework load_balance

On 26/07/2019 15:47, Vincent Guittot wrote:
[...]
>> If CPU0 runs the load balancer, balancing utilization would mean pulling
>> 2 tasks from CPU1 to reach the domain-average of 40%. The good side of this
>> is that we could save ourselves from running some newidle balances, but
>> I'll admit that's all quite "finger in the air".
> 
> Don't forget that scheduler also selects a cpu when task wakeup and
> should cope with such situation
> 

Right, although I'm not sure even the slow wakeup path is any good at
balancing utilization.

>>
>>>> happen, but it'd be a shame to repeatedly do this when we could
>>>> preemptively balance utilization.
>>>>