linux-kernel - [CHANGE 1/2] sched/isolation: Make use of more than one housekeeping cpu

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Message-ID: <20250211140104.420739-1-pauld@redhat.com>
Date: Tue, 11 Feb 2025 14:01:04 +0000
From: Phil Auld <pauld@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Waiman Long <longman@...hat.com>
Subject: [CHANGE 1/2] sched/isolation: Make use of more than one housekeeping cpu

The exising code uses housekeeping_any_cpu() to select a cpu for
a given housekeeping task. However, this often ends up calling
cpumask_any_and() which is defined as cpumask_first_and() which has
the effect of alyways using the first cpu among those available.

The same applies when multiple NUMA nodes are involved. In that
case the first cpu in the local node is chosen which does provide
a bit of spreading but with multiple HK cpus per node the same
issues arise.

Spread the HK work out by having housekeeping_any_cpu() and
sched_numa_find_closest() use cpumask_any_and_distribute()
instead of cpumask_any_and().

Signed-off-by: Phil Auld <pauld@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Frederic Weisbecker <frederic@...nel.org>
Cc: Waiman Long <longman@...hat.com>
Cc: linux-kernel@...r.kernel.org
---
 kernel/sched/isolation.c | 2 +-
 kernel/sched/topology.c  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 81bc8b329ef1..93b038d48900 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -40,7 +40,7 @@ int housekeeping_any_cpu(enum hk_type type)
 			if (cpu < nr_cpu_ids)
 				return cpu;
 
-			cpu = cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask);
+			cpu = cpumask_any_and_distribute(housekeeping.cpumasks[type], cpu_online_mask);
 			if (likely(cpu < nr_cpu_ids))
 				return cpu;
 			/*
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index c49aea8c1025..94133f843485 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2101,7 +2101,7 @@ int sched_numa_find_closest(const struct cpumask *cpus, int cpu)
 	for (i = 0; i < sched_domains_numa_levels; i++) {
 		if (!masks[i][j])
 			break;
-		cpu = cpumask_any_and(cpus, masks[i][j]);
+		cpu = cpumask_any_and_distribute(cpus, masks[i][j]);
 		if (cpu < nr_cpu_ids) {
 			found = cpu;
 			break;
-- 
2.47.1