linux-kernel - [PATCH 0/2 v5] Reintroduce 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-next>] [day] [month] [year] [list]

Message-ID: <20251112122521.1331238-1-mgorman@techsingularity.net>
Date: Wed, 12 Nov 2025 12:25:19 +0000
From: Mel Gorman <mgorman@...hsingularity.net>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Valentin Schneider <vschneid@...hat.com>,
	Chris Mason <clm@...a.com>,
	Madadi Vineeth Reddy <vineethr@...ux.ibm.com>,
	linux-kernel@...r.kernel.org,
	Mel Gorman <mgorman@...hsingularity.net>
Subject: [PATCH 0/2 v5] Reintroduce NEXT_BUDDY for EEVDF

Changes since v4
o Splitout decisions into separate functions			(peterz)
o Flow clarity							(peterz)

Changes since v3
o Place new code near first consumer				(peterz)
o Separate between PREEMPT_SHORT and NEXT_BUDDY			(peterz)
o Naming and code flow clarity					(peterz)
o Restore slice protection					(peterz)

Changes since v2
o Review feedback applied from Prateek

I've been chasing down a number of schedule issues recently like many
others and found they were broadly grouped as

1. Failure to boost CPU frequency with powersave/ondemand governors
2. Processors entering idle states that are too deep
3. Differences in wakeup latencies for wakeup-intensive workloads

Adding topology into account means that there is a lot of machine-specific
behaviour which may explain why some discussions recently have reproduction
problems. Nevertheless, the removal of LAST_BUDDY and NEXT_BUDDY being
disabled has an impact on wakeup latencies.

This series enables NEXT_BUDDY and may select a wakee if it's eligible to
run even though other unrelated tasks may have an earlier deadline.

Mel Gorman (2):
  sched/fair: Enable scheduler feature NEXT_BUDDY
  sched/fair: Reimplement NEXT_BUDDY to align with EEVDF goals

 kernel/sched/fair.c     | 152 ++++++++++++++++++++++++++++++++++------
 kernel/sched/features.h |   2 +-
 2 files changed, 131 insertions(+), 23 deletions(-)

-- 
2.51.0