linux-kernel - [PATCH] sched_ext: idle: Skip cross-node search with !CONFIG

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Message-ID: <20250603082201.173642-1-arighi@nvidia.com>
Date: Tue,  3 Jun 2025 10:22:01 +0200
From: Andrea Righi <arighi@...dia.com>
To: Tejun Heo <tj@...nel.org>,
	David Vernet <void@...ifault.com>,
	Changwoo Min <changwoo@...lia.com>
Cc: Yury Norov <yury.norov@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] sched_ext: idle: Skip cross-node search with !CONFIG_NUMA

In the idle CPU selection logic, attempting cross-node searches adds
unnecessary complexity when CONFIG_NUMA is disabled.

Since there's no meaningful concept of nodes in this case, simplify the
logic by restricting the idle CPU search to the current node only.

Fixes: 48849271e6611 ("sched_ext: idle: Per-node idle cpumasks")
Signed-off-by: Andrea Righi <arighi@...dia.com>
---
 kernel/sched/ext_idle.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c
index 66da03cc0b338..8660d9ae40169 100644
--- a/kernel/sched/ext_idle.c
+++ b/kernel/sched/ext_idle.c
@@ -138,6 +138,7 @@ static s32 pick_idle_cpu_in_node(const struct cpumask *cpus_allowed, int node, u
 		goto retry;
 }
 
+#ifdef CONFIG_NUMA
 /*
  * Tracks nodes that have not yet been visited when searching for an idle
  * CPU across all available nodes.
@@ -186,6 +187,13 @@ static s32 pick_idle_cpu_from_online_nodes(const struct cpumask *cpus_allowed, i
 
 	return cpu;
 }
+#else
+static inline s32
+pick_idle_cpu_from_online_nodes(const struct cpumask *cpus_allowed, int node, u64 flags)
+{
+	return -EBUSY;
+}
+#endif
 
 /*
  * Find an idle CPU in the system, starting from @node.
-- 
2.49.0