linux-kernel - Re: [PATCH RFC 3/8] sched/ext: Add a DL server for sched

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: <20250317103101.GC34541@noisy.programming.kicks-ass.net>
Date: Mon, 17 Mar 2025 11:31:01 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Joel Fernandes <joelagnelf@...dia.com>
Cc: linux-kernel@...r.kernel.org, Andrea Righi <arighi@...dia.com>,
	Tejun Heo <tj@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	David Vernet <void@...ifault.com>,
	Changwoo Min <changwoo@...lia.com>,
	Luigi De Matteis <ldematteis123@...il.com>, paulmck@...nel.org,
	boqun.feng@...il.com
Subject: Re: [PATCH RFC 3/8] sched/ext: Add a DL server for sched_ext tasks

On Sat, Mar 15, 2025 at 07:15:27PM -0400, Joel Fernandes wrote:
> 
> 
> On 3/15/2025 3:22 AM, Peter Zijlstra wrote:
> > On Fri, Mar 14, 2025 at 10:21:50PM -0400, Joel Fernandes wrote:
> >> sched_ext currently suffers starvation due to RT. The same workload when
> >> converted to EXT can get zero runtime if RT is 100% running, causing EXT
> >> processes to stall. Fix it by adding a DL server for EXT.
> > 
> > This needs a lot more words on why you need a second server. Because I
> > don't think you do.
> 
> Sure, I will add more words to the change log to explain rationale. When you say
> "I don't think you do", do you mean that both FAIR and EXT could be served by
> the same server? 

Yeah, because now you get two deadline entities both having a
reservation on bandwidth. One of which is not going to be used -- this
is not nice.

> If so, that will not handle the case where the system has both
> FAIR and EXT tasks in the mix (EXT has a partial mode where certain tasks can be
> made EXT with certain others left as FAIR) and FAIR runs 100% and starves EXT.

Well, you did not mention that issue, you only babbled about RT.

I did point out that issue with ext, and TJ said this mixed mode wasn't
really meant to be used or somesuch.

So if that's changed, this needs a separate discussion.

Also; I gotta ask, why is nvidia looking at ext ?