linux-kernel - [PATCH v2 3/3] sched/fair: Ensure select housekeeping cpus in task_numa_find

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Message-Id: <20250103065930.413464-4-zhouchuyi@bytedance.com>
Date: Fri,  3 Jan 2025 14:59:30 +0800
From: Chuyi Zhou <zhouchuyi@...edance.com>
To: mingo@...hat.com,
	peterz@...radead.org,
	juri.lelli@...hat.com,
	vincent.guittot@...aro.org,
	dietmar.eggemann@....com,
	rostedt@...dmis.org,
	bsegall@...gle.com,
	mgorman@...e.de,
	vschneid@...hat.com,
	longman@...hat.com,
	riel@...riel.com
Cc: chengming.zhou@...ux.dev,
	kprateek.nayak@....com,
	linux-kernel@...r.kernel.org,
	Chuyi Zhou <zhouchuyi@...edance.com>
Subject: [PATCH v2 3/3] sched/fair: Ensure select housekeeping cpus in task_numa_find_cpu

Now in task_numa_find_cpu(), we only skip CPUs that are not in the task's
cpumask, which could result in migrating the task to an isolated domain if
the task's cpumask includes isolated CPUs. This is because cpuset
configured partitions are always reflected in each member task's cpumask.
However, for isolcpus= kernel command line option, the isolated CPUs are
simply omitted from sched_domains without further restrictions on tasks'
cpumasks.

This change replaces the set of CPUs allowed to migrate the task from
p->cpus_ptr by the intersection of p->cpus_ptr and
housekeeping_cpumask(HK_TYPE_DOMAIN).

Signed-off-by: Chuyi Zhou <zhouchuyi@...edance.com>
---
 kernel/sched/fair.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a0139659fe7a..05782b563609 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2081,6 +2081,12 @@ numa_type numa_classify(unsigned int imbalance_pct,
 	return node_fully_busy;
 }
 
+static inline bool numa_migrate_test_cpu(struct task_struct *p, int cpu)
+{
+	return cpumask_test_cpu(cpu, p->cpus_ptr) &&
+			housekeeping_cpu(cpu, HK_TYPE_DOMAIN);
+}
+
 #ifdef CONFIG_SCHED_SMT
 /* Forward declarations of select_idle_sibling helpers */
 static inline bool test_idle_cores(int cpu);
@@ -2168,7 +2174,7 @@ static void task_numa_assign(struct task_numa_env *env,
 		/* Find alternative idle CPU. */
 		for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start + 1) {
 			if (cpu == env->best_cpu || !idle_cpu(cpu) ||
-			    !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
+			    !numa_migrate_test_cpu(env->p, cpu)) {
 				continue;
 			}
 
@@ -2480,7 +2486,7 @@ static void task_numa_find_cpu(struct task_numa_env *env,
 
 	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
 		/* Skip this CPU if the source task cannot migrate */
-		if (!cpumask_test_cpu(cpu, env->p->cpus_ptr))
+		if (!numa_migrate_test_cpu(env->p, cpu))
 			continue;
 
 		env->dst_cpu = cpu;
-- 
2.20.1