From: Peter Zijlstra <peterz@infradead.org>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Valentin Schneider <vschneid@redhat.com>,
Chris Mason <clm@meta.com>
Subject: Re: [PATCH 1/2] sched/fair: Enable scheduler feature NEXT_BUDDY
Date: Tue, 28 Oct 2025 15:37:38 +0100 [thread overview]
Message-ID: <20251028143738.GB4067720@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20251027133915.4103633-2-mgorman@techsingularity.net>
On Mon, Oct 27, 2025 at 01:39:14PM +0000, Mel Gorman wrote:
> NEXT_BUDDY has been disabled since commit 0ec9fab3d186 ("sched: Improve
> latencies and throughput") and LAST_BUDDY was removed in commit 5e963f2bd465
> ("sched/fair: Commit to EEVDF"). The reasoning is not clear but as vruntime
> spread is mentioned so the expectation is that NEXT_BUDDY had an impact
> on overall fairness. It was not noted why LAST_BUDDY was removed but it
> is assumed that it's very difficult to reason what LAST_BUDDY's correct
> and effective behaviour should be while still respecting EEVDFs goals.
I think I was just struggling to make sense of things and figured
less is more and axed it.
I have vague memories trying to work through the dynamics of a
wakeup-stack and the EEVDF latency requirements and getting a head-ache.
next prev parent reply other threads:[~2025-10-28 14:37 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20251027133915.4103633-1-mgorman@techsingularity.net>
2025-10-27 13:39 ` Mel Gorman
2025-10-28 14:37 ` Peter Zijlstra [this message]
2025-10-27 13:39 ` [PATCH 2/2] sched/fair: Reimplement NEXT_BUDDY to align with EEVDF goals Mel Gorman
2025-10-28 15:05 ` Peter Zijlstra
2025-10-31 9:46 ` Mel Gorman
2025-10-28 15:09 ` Peter Zijlstra
2025-10-31 9:48 ` Mel Gorman
2025-10-28 15:33 ` Peter Zijlstra
2025-10-28 15:47 ` Peter Zijlstra
2025-10-30 9:10 ` Peter Zijlstra
2025-10-31 10:27 ` Mel Gorman
2025-11-12 12:25 [PATCH 0/2 v5] Reintroduce NEXT_BUDDY for EEVDF Mel Gorman
2025-11-12 12:25 ` [PATCH 1/2] sched/fair: Enable scheduler feature NEXT_BUDDY Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2025-11-03 11:04 [PATCH 0/2 v4] Reintroduce NEXT_BUDDY for EEVDF Mel Gorman
2025-11-03 11:04 ` [PATCH 1/2] sched/fair: Enable scheduler feature NEXT_BUDDY Mel Gorman
2025-10-21 14:28 [RFC PATCH 0/2] Reintroduce NEXT_BUDDY for EEVDF v2 Mel Gorman
2025-10-21 14:28 ` [PATCH 1/2] sched/fair: Enable scheduler feature NEXT_BUDDY Mel Gorman
[not found] <20250714134429.19624-1-mgorman@techsingularity.net>
2025-07-14 13:44 ` Mel Gorman
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