linux-kernel - Re: [PATCH v3 4/5] sched/pelt: Add a new runnable average signal

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]

Message-ID: <20200219140216.GP3466@techsingularity.net>
Date:   Wed, 19 Feb 2020 14:02:17 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
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,
        parth@...ux.ibm.com, valentin.schneider@....com, hdanton@...a.com
Subject: Re: [PATCH v3 4/5] sched/pelt: Add a new runnable average signal

On Wed, Feb 19, 2020 at 01:55:13PM +0100, Vincent Guittot wrote:
> Now that runnable_load_avg has been removed, we can replace it by a new
> signal that will highlight the runnable pressure on a cfs_rq. This signal
> track the waiting time of tasks on rq and can help to better define the
> state of rqs.
> 
> At now, only util_avg is used to define the state of a rq:
>   A rq with more that around 80% of utilization and more than 1 tasks is
>   considered as overloaded.
> 
> But the util_avg signal of a rq can become temporaly low after that a task
> migrated onto another rq which can bias the classification of the rq.
> 
> When tasks compete for the same rq, their runnable average signal will be
> higher than util_avg as it will include the waiting time and we can use
> this signal to better classify cfs_rqs.
> 
> The new runnable_avg will track the runnable time of a task which simply
> adds the waiting time to the running time. The runnable _avg of cfs_rq
> will be the /Sum of se's runnable_avg and the runnable_avg of group entity
> will follow the one of the rq similarly to util_avg.
> 
> Tested-by: Valentin Schneider <valentin.schneider@....com>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>

Thanks.

Picked up and included in "Reconcile NUMA balancing decisions with the
load balancer v4". The only change I made to your patches was move the
reintroduction of cpu_runnable to the patch that requires it to avoid a
build warning.

-- 
Mel Gorman
SUSE Labs