From: Peter Zijlstra <peterz@infradead.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>,
Tejun Heo <tj@kernel.org>, David Vernet <void@manifault.com>,
Changwoo Min <changwoo@igalia.com>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
Vladimir Vdovin <deliran@verdict.gg>,
Gregory Price <gourry@gourry.net>,
David Dai <david.dai@linux.dev>, Emil Tsalapatis <etsal@meta.com>,
Christian Loehle <christian.loehle@arm.com>,
Balbir Singh <balbirs@nvidia.com>,
Lee Trager <ltrager@nvidia.com>,
sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/6] sched_ext: Add a kfunc to read a task's preferred NUMA node
Date: Tue, 27 Oct 2026 12:54:10 +0100 [thread overview]
Message-ID: <20261027115410.GK2668564@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <auCJHU4_ugxayy7i@gpd4>
On Tue, Oct 27, 2026 at 12:21:01PM +0100, Andrea Righi wrote:
> > But should we not cleanup first and then add shiny on top?
>
> Fair enough. Looking more closely, I think there're only two places in
> fair that still use p->numa_preferred_nid when NUMA balancing is
> disabled at runtime: find_idlest_group() and the fbq classification in
> the load balancer (via rq->nr_numa_running / nr_preferred_running).
> Everything else is already gated by sched_numa_balancing.
>
> Assuming I'm not missing anything, we can probably add a preparatory
> patch that gates those two on sched_numa_balancing as well, then make
> scx_bpf_task_numa_nid() return NUMA_NO_NODE when NUMA balancing is
> disabled. In this way the stale value is never used.
Sounds like a plan :-)
next prev parent reply other threads:[~2026-10-27 11:54 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-27 4:13 [PATCHSET v2 sched_ext/for-7.5] sched_ext: Add NUMA balancing support Andrea Righi
2026-10-27 4:13 ` [PATCH 1/6] sched/numa: Let other scheduling classes drive NUMA scanning Andrea Righi
2026-10-27 4:13 ` [PATCH 2/6] sched/numa: Leave the placement of a BPF-scheduled task to its scheduler Andrea Righi
2026-10-27 5:45 ` K Prateek Nayak
2026-10-27 6:43 ` Andrea Righi
2026-10-27 9:00 ` K Prateek Nayak
2026-10-27 9:30 ` Andrea Righi
2026-10-27 10:43 ` Peter Zijlstra
2026-10-27 11:09 ` Andrea Righi
2026-10-27 11:52 ` Peter Zijlstra
2026-10-27 4:13 ` [PATCH 3/6] sched/numa: Notify the scheduling class of preferred node changes Andrea Righi
2026-10-27 5:30 ` K Prateek Nayak
2026-10-27 6:34 ` Andrea Righi
2026-10-27 8:02 ` K Prateek Nayak
2026-10-27 4:13 ` [PATCH 4/6] sched_ext: Report preferred NUMA nodes through ops.set_numa_node() Andrea Righi
2026-10-27 10:49 ` Peter Zijlstra
2026-10-27 11:14 ` Andrea Righi
2026-10-27 4:13 ` [PATCH 5/6] sched_ext: Add a kfunc to read a task's preferred NUMA node Andrea Righi
2026-10-27 6:12 ` K Prateek Nayak
2026-10-27 6:57 ` Andrea Righi
2026-10-27 10:50 ` Peter Zijlstra
2026-10-27 11:21 ` Andrea Righi
2026-10-27 11:54 ` Peter Zijlstra [this message]
2026-10-27 4:13 ` [PATCH 6/6] selftests/sched_ext: Test preferred NUMA node notifications Andrea Righi
2026-10-27 10:52 ` [PATCHSET v2 sched_ext/for-7.5] sched_ext: Add NUMA balancing support Peter Zijlstra
2026-10-27 11:38 ` Andrea Righi
2026-10-27 11:55 ` Peter Zijlstra
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