Merge: sched/isolation: Make use of more than one housekeeping cpu

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/993

JIRA: https://issues.redhat.com/browse/RHEL-8694

commit 6432e16
Author: Phil Auld <pauld@redhat.com>
Date:   Tue Feb 18 18:46:18 2025 +0000

    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.

    We have numerous cases where a single HK cpu just cannot keep up
    and the remote_tick warning fires. It also can lead to the other
    things (orchastration sw, HA keepalives etc) on the HK cpus getting
    starved which leads to other issues.  In these cases we recommend
    increasing the number of HK cpus.  But... that only helps the
    userspace tasks somewhat. It does not help the actual housekeeping
    part.

    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@redhat.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Reviewed-by: Waiman Long <longman@redhat.com>
    Reviewed-by: Vishal Chourasia <vishalc@linux.ibm.com>
    Acked-by: Frederic Weisbecker <frederic@kernel.org>
    Link: https://lore.kernel.org/r/20250218184618.1331715-1-pauld@redhat.com

Signed-off-by: Phil Auld <pauld@redhat.com>

Approved-by: Herton R. Krzesinski <herton@redhat.com>
Approved-by: Waiman Long <longman@redhat.com>
Approved-by: Juri Lelli <juri.lelli@redhat.com>
Approved-by: Wander Lairson Costa <wander@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Jan Stancek <jstancek@redhat.com>

Author: jstancek

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;
 			/*

kernel/sched/topology.c

@@ -2109,7 +2109,7 @@ 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;