linux-kernel - Re: [PATCH 4/6 v8] sched/fair: Add push task mechanism for fair

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] [day] [month] [year] [list]

Message-ID: <65105f45-091d-461b-88e1-0c4c1940927e@amd.com>
Date: Sat, 6 Dec 2025 08:38:59 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Vincent Guittot <vincent.guittot@...aro.org>
CC: Peter Zijlstra <peterz@...radead.org>, <mingo@...hat.com>,
	<juri.lelli@...hat.com>, <dietmar.eggemann@....com>, <rostedt@...dmis.org>,
	<bsegall@...gle.com>, <mgorman@...e.de>, <vschneid@...hat.com>,
	<linux-kernel@...r.kernel.org>, <pierre.gondois@....com>,
	<qyousef@...alina.io>, <hongyan.xia2@....com>, <christian.loehle@....com>,
	<luis.machado@....com>
Subject: Re: [PATCH 4/6 v8] sched/fair: Add push task mechanism for fair

On 12/5/2025 7:06 PM, Vincent Guittot wrote:
>> So I was experimenting with:
>>
>>     deactivate_task(rq, p, 0);
>>     set_task_cpu(p, target_cpu);
>>     __ttwu_queue_wakelist(p, target_cpu, 0);
>>
>> and nothing has screamed at me yet during the benchmark runs.
>> Would this be any good instead of the whole lock juggling?
>>
>> Since this CPU is found to be going overloaded, pushing via an
> 
> Just to make sure that we speak about the same thing. With EAS
> overloaded and overutilized are 2 different things. EAS don't care and
> some time want to overload a CPU( having more than1 task on the CPU)
> but EAS is diable once teh CPU becomes overutilized

I meant to say overutilized in this context. Sorry about that.

> 
>> IPI vs taking the overhead ourselves seems to make more sense
>> to me from EAS standpoint.
> 
> I suppose that it's worth trying the IPI on EAS and embedded device

If they are cheap enough, we can simply use TTWU_QUEUE check for the
!PREEMPT_RT and use move queued task otherwise.

-- 
Thanks and Regards,
Prateek