From: Mel Gorman Date: Tue, 20 Jan 2026 11:33:35 +0000 (+0000) Subject: sched/fair: Disable scheduler feature NEXT_BUDDY X-Git-Tag: v6.19-rc7~13^2~1 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4f70f106bca1a56bd66d00830ac91680bd754974;p=thirdparty%2Fkernel%2Flinux.git sched/fair: Disable scheduler feature NEXT_BUDDY NEXT_BUDDY was disabled with the introduction of EEVDF and enabled again after NEXT_BUDDY was rewritten for EEVDF by commit e837456fdca8 ("sched/fair: Reimplement NEXT_BUDDY to align with EEVDF goals"). It was not expected that this would be a universal win without a crystal ball instruction but the reported regressions are a concern [1][2] even if gains were also reported. Specifically; o mysql with client/server running on different servers regresses o specjbb reports lower peak metrics o daytrader regresses The mysql is realistic and a concern. It needs to be confirmed if specjbb is simply shifting the point where peak performance is measured but still a concern. daytrader is considered to be representative of a real workload. Access to test machines is currently problematic for verifying any fix to this problem. Disable NEXT_BUDDY for now by default until the root causes are addressed. Signed-off-by: Mel Gorman Signed-off-by: Peter Zijlstra (Intel) Tested-by: Madadi Vineeth Reddy Link: https://lore.kernel.org/lkml/4b96909a-f1ac-49eb-b814-97b8adda6229@arm.com [1] Link: https://lore.kernel.org/lkml/ec3ea66f-3a0d-4b5a-ab36-ce778f159b5b@linux.ibm.com [2] Link: https://patch.msgid.link/fyqsk63pkoxpeaclyqsm5nwtz3dyejplr7rg6p74xwemfzdzuu@7m7xhs5aqpqw --- diff --git a/kernel/sched/features.h b/kernel/sched/features.h index 980d92bab8ab..136a6584be79 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -29,7 +29,7 @@ SCHED_FEAT(PREEMPT_SHORT, true) * wakeup-preemption), since its likely going to consume data we * touched, increases cache locality. */ -SCHED_FEAT(NEXT_BUDDY, true) +SCHED_FEAT(NEXT_BUDDY, false) /* * Allow completely ignoring cfs_rq->next; which can be set from various