linux-kernel - Re: [PATCH 1/4 v2] sched/fair: relax constraint on task's load during load balance

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 23 Sep 2020 15:43:19 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, linux-kernel@...r.kernel.org, pauld@...hat.com,
        hdanton@...a.com
Subject: Re: [PATCH 1/4 v2] sched/fair: relax constraint on task's load during load balance


On 21/09/20 08:24, Vincent Guittot wrote:
> Some UCs like 9 always running tasks on 8 CPUs can't be balanced and the
> load balancer currently migrates the waiting task between the CPUs in an
> almost random manner. The success of a rq pulling a task depends of the
> value of nr_balance_failed of its domains and its ability to be faster
> than others to detach it. This behavior results in an unfair distribution
> of the running time between tasks because some CPUs will run most of the
> time, if not always, the same task whereas others will share their time
> between several tasks.
>
> Instead of using nr_balance_failed as a boolean to relax the condition
> for detaching task, the LB will use nr_balanced_failed to relax the
> threshold between the tasks'load and the imbalance. This mecanism
> prevents the same rq or domain to always win the load balance fight.
>
> Reviewed-by: Phil Auld <pauld@...hat.com>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>

Reviewed-by: Valentin Schneider <valentin.schneider@....com>