linux-kernel - [PATCH 08/10] sched_ext: idle: introduce SCX_PICK_IDLE

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Message-ID: <20241220154107.287478-9-arighi@nvidia.com>
Date: Fri, 20 Dec 2024 16:11:40 +0100
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>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 08/10] sched_ext: idle: introduce SCX_PICK_IDLE_NODE

Introduce a flag to restrict the selection of an idle CPU to a specific
NUMA node.

Signed-off-by: Andrea Righi <arighi@...dia.com>
---
 kernel/sched/ext.c      |  1 +
 kernel/sched/ext_idle.c | 11 +++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 143938e935f1..da5c15bd3c56 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -773,6 +773,7 @@ enum scx_deq_flags {
 
 enum scx_pick_idle_cpu_flags {
 	SCX_PICK_IDLE_CORE	= 1LLU << 0,	/* pick a CPU whose SMT siblings are also idle */
+	SCX_PICK_IDLE_NODE	= 1LLU << 1,	/* pick a CPU in the same target NUMA node */
 };
 
 enum scx_kick_flags {
diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c
index 444f2a15f1d4..013deaa08f12 100644
--- a/kernel/sched/ext_idle.c
+++ b/kernel/sched/ext_idle.c
@@ -199,6 +199,12 @@ static s32 scx_pick_idle_cpu(const struct cpumask *cpus_allowed, int node, u64 f
 		cpu = pick_idle_cpu_from_node(cpus_allowed, n, flags);
 		if (cpu >= 0)
 			break;
+		/*
+		 * Check if the search is restricted to the same core or
+		 * the same node.
+		 */
+		if (flags & SCX_PICK_IDLE_NODE)
+			break;
 	}
 
 	return cpu;
@@ -495,7 +501,8 @@ static s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
 		 * Search for any fully idle core in the same LLC domain.
 		 */
 		if (llc_cpus) {
-			cpu = pick_idle_cpu_from_node(llc_cpus, node, SCX_PICK_IDLE_CORE);
+			cpu = scx_pick_idle_cpu(llc_cpus, node,
+						SCX_PICK_IDLE_CORE | SCX_PICK_IDLE_NODE);
 			if (cpu >= 0)
 				goto cpu_found;
 		}
@@ -533,7 +540,7 @@ static s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
 	 * Search for any idle CPU in the same LLC domain.
 	 */
 	if (llc_cpus) {
-		cpu = pick_idle_cpu_from_node(llc_cpus, node, 0);
+		cpu = scx_pick_idle_cpu(llc_cpus, node, SCX_PICK_IDLE_NODE);
 		if (cpu >= 0)
 			goto cpu_found;
 	}
-- 
2.47.1