git: 06ffb01fa0 - main - Status/2026Q2/scheduler.adoc: Add report

The branch main has been updated by olce:

URL: https://cgit.FreeBSD.org/doc/commit/?id=06ffb01fa0c9306bf28e6bbd4e0d3426e2746257

commit 06ffb01fa0c9306bf28e6bbd4e0d3426e2746257
Author:     Olivier Certner <olce@FreeBSD.org>
AuthorDate: 2026-07-06 12:58:52 +0000
Commit:     Olivier Certner <olce@FreeBSD.org>
CommitDate: 2026-07-14 15:19:07 +0000

    Status/2026Q2/scheduler.adoc: Add report
    
    Reviewed by:    salvadore
    Discussed with: Graham Percival <gperciva_tarsnap.com>
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D58051
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+=== Scheduler
+
+Links: +
+link:https://wiki.freebsd.org/DevSummit/202606[DevSummit Wiki page] URL: https://wiki.freebsd.org/DevSummit/202606 +
+link:https://wiki.freebsd.org/DevSummit/202606?action=AttachFile&do=view&target=Scheduler.pdf[Slides] URL: https://wiki.freebsd.org/DevSummit/202606?action=AttachFile&do=view&target=Scheduler.pdf
+
+Contact: Olivier Certner <olce@FreeBSD.org>
+
+Ongoing work is happening in the area of schedulers along multiple axes.
+
+We are working on solutions to long-standing shortcomings in the ULE scheduler such as unfairness for non-interactive threads in certain particular circumstances and the very weak effect of nice values.
+It seems difficult to solve the first in full with ULE's current design, so in parallel we have been sketching a new design with the following additional aims:
+
+1. More stable and predictable behavior.
+2. Separately controllable latency and allocated CPU.
+3. Enabling new features like scheduling on hybrid CPUs, power-aware scheduling, hierarchical scheduling, etc. while retaining fairness.
+
+We have also been reviewing the 4BSD and ULE schedulers in detail, leading to some bug fixes, such as:
+
+- Priority conflation of differently-niced CPU-bound threads (4BSD)
+- Priority diminishing too slowly when consuming CPU, because of some obsolete SMP scaling (4BSD)
+- Fix off by one in `preempt_thresh` parameter definition (ULE)
+- Fix selecting lowest priority thread early in some corner cases (ULE)
+- Stop consuming memory linearly with `MAXCPU` for local runqueues (4BSD; by Minsoo Choo).
+
+A presentation was done at BSDCan 2026's Developer Summit on these matters (see link at the top).
+
+On the hybrid scheduling front, a number of reviews have been created by Koine Yuusuke with code to support Intel Hardware Feedback Interface (HFI) and Thread Director (ITD), and a common infrastructure for capacities and scores was proposed by Minsoo Choo.
+We will review and shepherd these submissions.
+
+Sponsor: The FreeBSD Foundation