Re: [PATCH v2] [tip: sched/core] sched: Move PLACE_LAG and RUN_TO_PARITY to sysctl
From: Peter Zijlstra <peterz@infradead.org>
Date: 2025-02-12 09:17:30
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On Tue, Feb 11, 2025 at 11:36:44PM -0600, Cristian Prundeanu wrote:
Replacing CFS with the EEVDF scheduler in kernel 6.6 introduced significant performance degradation in multiple database-oriented workloads. This degradation manifests in all kernel versions using EEVDF, across multiple Linux distributions, hardware architectures (x86_64, aarm64, amd64), and CPU generations. Testing combinations of available scheduler features showed that the largest improvement (short of disabling all EEVDF features) came from disabling both PLACE_LAG and RUN_TO_PARITY. Moving PLACE_LAG and RUN_TO_PARITY to sysctl will allow users to override their default values and persist them with established mechanisms.
Nope -- you have knobs in debugfs, and that's where they'll stay. Esp. PLACE_LAG is super dodgy and should not get elevated to anything remotely official. Also, FYI, by keeping these emails threaded in the old thread I nearly missed them again. I'm not sure where this nonsense of keeping everything in one thread came from, but it is bloody stupid.