linux-kernel - Re: [PATCH v3 4/6] sched/fair: Limit run to parity to the min slice of enqueued entities

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: <20250710123435.GM1613376@noisy.programming.kicks-ass.net>
Date: Thu, 10 Jul 2025 14:34:35 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>, mingo@...hat.com,
	juri.lelli@...hat.com, dietmar.eggemann@....com,
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
	vschneid@...hat.com, dhaval@...nis.ca, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/6] sched/fair: Limit run to parity to the min slice
 of enqueued entities


> > If I set my task’s custom slice to a larger value but another task has a smaller slice,
> > this change will cap my protected window to the smaller slice. Does that mean my custom
> > slice is no longer honored?
> 
> What do you mean by honored ? EEVDF never mandates that a request of
> size slice will be done in one go. Slice mainly defines the deadline
> and orders the entities but not that it will always run your slice in
> one go. Run to parity tries to minimize the number of context switches
> between runnable tasks but must not break fairness and lag theorem.So
> If your task A has a slice of 10ms and task B wakes up with a slice of
> 1ms. B will preempt A because its deadline is earlier. If task B still
> wants to run after its slice is exhausted, it will not be eligible and
> task A will run until task B becomes eligible, which is as long as
> task B's slice.

Right. Added if you don't want wakeup preemption, we've got SCHED_BATCH
for you.