linux-kernel - Re: [PATCH] sched/fair: Force idle aware load balancing

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20251201130224.274217-1-sieberf@amazon.com>
Date: Mon, 1 Dec 2025 15:02:23 +0200
From: Fernand Sieber <sieberf@...zon.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: Vincent Guittot <vincent.guittot@...aro.org>, <mingo@...hat.com>,
	<linux-kernel@...r.kernel.org>, <juri.lelli@...hat.com>,
	<dietmar.eggemann@....com>, <rostedt@...dmis.org>, <bsegall@...gle.com>,
	<mgorman@...e.de>, <vschneid@...hat.com>, <kprateek.nayak@....com>,
	<dwmw@...zon.co.uk>, <jschoenh@...zon.de>, <liuyuxua@...zon.com>,
	<abusse@...zon.com>, <gmazz@...zon.com>, <rkagan@...zon.com>,
	<nh-open-source@...zon.com>
Subject: Re: [PATCH] sched/fair: Force idle aware load balancing

On Fri, 28 Nov 2025 at 14:58, Peter Zijlstra <peterz@...radead.org> wrote:
> On Fri, Nov 28, 2025 at 02:55:36PM +0100, Vincent Guittot wrote:
> > On Thu, 27 Nov 2025 at 21:28, Fernand Sieber <sieberf@...zon.com> wrote:
>
> > > @@ -10135,15 +10136,15 @@ static inline int sg_imbalanced(struct sched_group *group)
> > >  static inline bool
> > >  group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
> > >  {
> > > -       if (sgs->sum_nr_running < sgs->group_weight)
> > > +       if (sgs->sum_nr_running < (sgs->group_weight - sgs->forceidle_weight))
> > >                 return true;
> > >
> > > -       if ((sgs->group_capacity * imbalance_pct) <
> > > -                       (sgs->group_runnable * 100))
> > > +       if ((sgs->group_capacity * imbalance_pct * (sgs->group_weight - sgs->forceidle_weight)) <
> > > +                       (sgs->group_runnable * 100 * sgs->group_weight))
> >
> > so you apply a ratio on group capacity based on the number of forced
> > idle but what if you have heterogeneous systems ?
>
> Ah, good point. I suppose tracking force_idle_capacity in
> update_sg_lb_stats() should be possible, and then subtract that from
> group_capacity or so.

Thanks. Addressed in rev2, by keeping track of both forceidle_weight and
forceidle_capacity:
https://lore.kernel.org/lkml/20251201124223.247107-1-sieberf@amazon.com/



Amazon Development Centre (South Africa) (Proprietary) Limited
29 Gogosoa Street, Observatory, Cape Town, Western Cape, 7925, South Africa
Registration Number: 2004 / 034463 / 07