linux-kernel - Re: [RFC PATCH] sched/feec: Simplify the traversal of pd'cpus

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: <CAB8ipk8kf1+Vd94wQn1XnWPvWqP1szxAeUroos1iV6Z17vbxFg@mail.gmail.com>
Date: Mon, 18 Aug 2025 19:05:20 +0800
From: Xuewen Yan <xuewen.yan94@...il.com>
To: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Christian Loehle <christian.loehle@....com>, Xuewen Yan <xuewen.yan@...soc.com>, mingo@...hat.com, 
	peterz@...radead.org, juri.lelli@...hat.com, vincent.guittot@...aro.org, 
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de, vschneid@...hat.com, 
	vdonnefort@...gle.com, ke.wang@...soc.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] sched/feec: Simplify the traversal of pd'cpus

On Fri, Aug 15, 2025 at 9:01 PM Dietmar Eggemann
<dietmar.eggemann@....com> wrote:
>
> On 14.08.25 10:52, Xuewen Yan wrote:
> > Hi Dietmar,
> >
> > On Thu, Aug 14, 2025 at 4:46 PM Dietmar Eggemann
> > <dietmar.eggemann@....com> wrote:
> >>
> >> On 12.08.25 10:33, Xuewen Yan wrote:
>
> [...]
>
> >> Can you not mask cpus already early in the pd loop (1) and then profit
> >> from (2) in these rare cases?
> >
> > I do not think the cpus_ptr chould place before the pd_cap calc,
> > because the following scenario should be considered:
> > the task's cpus_ptr cpus： 0,1,2,3
> > pd's cpus: 0,1,2,3,4,5,6
> > the pd's cap = cpu_cap * 6;
> > if we cpumask_and(pd'scpus, p->cpus_ptr),
> > the cpumask_weight = 4,
> > the pd's cap = cpu_cap *4.
>
> Yes, you're right! Missed this one.
>
> >> IIRC, the sd only plays a role here in
> >> exclusive cpusets scenarios which I don't thing anybody deploys with EAS?
> >
> > I am also wondering if the check for SD's CPUs could be removed...
>
> Still not 100% sure here. I would have to play with cpusets and EAS a
> little bit more. Are you thinking that in those cases p->cpus_ptr
> already covers the cpuset restriction so that the sd mask isn't necessary?

I am not familiar with cpuset, so I can't guarantee this. Similarly, I
also need to learn more about cpuset and cpu topology before I can
answer this question.

Thanks!