linux-kernel - Re: [REGRESSION] sched/fair: Reimplement NEXT

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: <20260112074703.GB830755@noisy.programming.kicks-ass.net>
Date: Mon, 12 Jan 2026 08:47:03 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Mel Gorman <mgorman@...hsingularity.net>,
	Dietmar Eggemann <dietmar.eggemann@....com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Aishwarya TCV <Aishwarya.TCV@....com>
Subject: Re: [REGRESSION] sched/fair: Reimplement NEXT_BUDDY to align with
 EEVDF goals

On Fri, Jan 09, 2026 at 10:15:46AM +0000, Ryan Roberts wrote:

> Here are the updated results, now including column for "revert #1 & #2".
> 
> 6-18-0 (base)		(baseline)
> 6-19-0-rc1		(New NEXT_BUDDY implementation enabled)
> revert #1 & #2		(NEXT_BUDDY disabled)
> revert #2		(Old NEXT_BUDDY implementation enabled)
> 
> 
> The regressions that are fixed by "revert #2" (as originally reported) are still 
> fixed in "revert #1 & #2". Interestingly, performance actually improves further 
> for the latter in the multi-node mysql benchmark (which is our VIP workload). 
> There are a couple of hackbench cases (sockets with high thread counts) that 
> showed an improvement with "revert #2" but which is gone with "revert #1 & #2".
> 
> Let me know if I can usefully do anything else.

If its not too much bother, could you run 6.19-rc with SCHED_BATCH ? The
defining characteristic of BATCH is that it fully ignores wakeup
preemption.