From: Mel Gorman <mgorman@techsingularity.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Juri Lelli <juri.lelli@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Phil Auld <pauld@redhat.com>, Hillf Danton <hdanton@sina.com>,
LKML <linux-kernel@vger.kernel.org>,
Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 11/13] sched/numa: Find an alternative idle CPU if the CPU is part of an active NUMA balance
Date: Wed, 19 Feb 2020 14:07:34 +0000 [thread overview]
Message-ID: <20200219140736.20499-12-mgorman@techsingularity.net> (raw)
In-Reply-To: <20200219140736.20499-1-mgorman@techsingularity.net>
Multiple tasks can attempt to select and idle CPU but fail because
numa_migrate_on is already set and the migration fails. Instead of failing,
scan for an alternative idle CPU. select_idle_sibling is not used because
it requires IRQs to be disabled and it ignores numa_migrate_on allowing
multiple tasks to stack. This scan may still fail if there are idle
candidate CPUs due to races but if this occurs, it's best that a task
stay on an available CPU that move to a contended one.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
kernel/sched/fair.c | 40 ++++++++++++++++++++++------------------
1 file changed, 22 insertions(+), 18 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b5c612f82de0..ce76f787353e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1624,15 +1624,34 @@ static void task_numa_assign(struct task_numa_env *env,
{
struct rq *rq = cpu_rq(env->dst_cpu);
- /* Bail out if run-queue part of active NUMA balance. */
- if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1))
+ /* Check if run-queue part of active NUMA balance. */
+ if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1)) {
+ int cpu;
+ int start = env->dst_cpu;
+
+ /* Find alternative idle CPU. */
+ for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start) {
+ if (cpu == env->best_cpu || !idle_cpu(cpu) ||
+ !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
+ continue;
+ }
+
+ env->dst_cpu = cpu;
+ rq = cpu_rq(env->dst_cpu);
+ if (!xchg(&rq->numa_migrate_on, 1))
+ goto assign;
+ }
+
+ /* Failed to find an alternative idle CPU */
return;
+ }
+assign:
/*
* Clear previous best_cpu/rq numa-migrate flag, since task now
* found a better CPU to move/swap.
*/
- if (env->best_cpu != -1) {
+ if (env->best_cpu != -1 && env->best_cpu != env->dst_cpu) {
rq = cpu_rq(env->best_cpu);
WRITE_ONCE(rq->numa_migrate_on, 0);
}
@@ -1806,21 +1825,6 @@ static void task_numa_compare(struct task_numa_env *env,
cpu = env->best_cpu;
}
- /*
- * Use select_idle_sibling if the previously found idle CPU is
- * not idle any more.
- */
- if (!idle_cpu(cpu)) {
- /*
- * select_idle_siblings() uses an per-CPU cpumask that
- * can be used from IRQ context.
- */
- local_irq_disable();
- cpu = select_idle_sibling(env->p, env->src_cpu,
- env->dst_cpu);
- local_irq_enable();
- }
-
env->dst_cpu = cpu;
}
--
2.16.4
next prev parent reply other threads:[~2020-02-19 14:09 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 14:07 [PATCH 00/13] Reconcile NUMA balancing decisions with the load balancer v5 Mel Gorman
2020-02-19 14:07 ` [PATCH 01/13] sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression Mel Gorman
2020-02-19 14:07 ` [PATCH 02/13] sched/numa: Trace when no candidate CPU was found on the preferred node Mel Gorman
2020-02-19 14:07 ` [PATCH 03/13] sched/numa: Distinguish between the different task_numa_migrate failure cases Mel Gorman
2020-02-19 14:07 ` [PATCH 04/13] sched/fair: Reorder enqueue/dequeue_task_fair path Mel Gorman
2020-02-19 14:07 ` [PATCH 05/13] sched/numa: Replace runnable_load_avg by load_avg Mel Gorman
2020-02-19 14:07 ` [PATCH 06/13] sched/numa: Use similar logic to the load balancer for moving between domains with spare capacity Mel Gorman
2020-02-19 14:07 ` [PATCH 07/13] sched/pelt: Remove unused runnable load average Mel Gorman
2020-02-19 14:07 ` [PATCH 08/13] sched/pelt: Add a new runnable average signal Mel Gorman
2020-02-19 14:07 ` [PATCH 09/13] sched/fair: Take into account runnable_avg to classify group Mel Gorman
2020-02-19 14:07 ` [PATCH 10/13] sched/numa: Prefer using an idle cpu as a migration target instead of comparing tasks Mel Gorman
2020-02-19 14:07 ` Mel Gorman [this message]
2020-02-19 14:07 ` [PATCH 12/13] sched/numa: Bias swapping tasks based on their preferred node Mel Gorman
2020-02-19 14:07 ` [PATCH 13/13] sched/numa: Stop an exhastive search if a reasonable swap candidate or idle CPU is found Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2020-02-24 9:52 [PATCH 00/13] Reconcile NUMA balancing decisions with the load balancer v6 Mel Gorman
2020-02-24 9:52 ` [PATCH 11/13] sched/numa: Find an alternative idle CPU if the CPU is part of an active NUMA balance Mel Gorman
2020-02-19 13:54 [PATCH 00/13] Reconcile NUMA balancing decisions with the load balancer v4 Mel Gorman
2020-02-19 13:54 ` [PATCH 11/13] sched/numa: Find an alternative idle CPU if the CPU is part of an active NUMA balance Mel Gorman
2020-02-17 10:43 [PATCH 00/13] Reconcile NUMA balancing decisions with the load balancer v3 Mel Gorman
2020-02-17 10:44 ` [PATCH 11/13] sched/numa: Find an alternative idle CPU if the CPU is part of an active NUMA balance Mel Gorman
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