linux-kernel - Re: [PATCH] sched, fair: Allow a small degree of load imbalance between SD

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: <20200107122943.GW2827@hirez.programming.kicks-ass.net>
Date:   Tue, 7 Jan 2020 13:29:43 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Ingo Molnar <mingo@...nel.org>, Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        Hillf Danton <hdanton@...a.com>,
        Parth Shah <parth@...ux.ibm.com>,
        Rik van Riel <riel@...riel.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched, fair: Allow a small degree of load imbalance
 between SD_NUMA domains v2

On Tue, Jan 07, 2020 at 11:42:11AM +0000, Mel Gorman wrote:
> On Tue, Jan 07, 2020 at 12:22:55PM +0100, Peter Zijlstra wrote:

> > > +		/* Consider allowing a small imbalance between NUMA groups */
> > > +		if (env->sd->flags & SD_NUMA) {
> > > +			struct sched_domain *child = env->sd->child;
> > 
> > This assumes sd-child exists, which should be true for NUMA domains I
> > suppose.
> > 
> 
> I would be stunned if it was not. What sort of NUMA domain would not have
> child domains? Does a memory-only NUMA node with no CPUs even generate
> a scheduler domain? If it does, then I guess the check is necessary.

I think it's fine, it was just my paranoia triggering. At the very least
we'll have the single CPU domain there.