From: Mel Gorman <mgorman@techsingularity.net>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.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>, LKML <linux-kernel@vger.kernel.org>,
Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 02/11] sched/fair: Optimize select_idle_core()
Date: Wed, 12 Feb 2020 09:36:45 +0000 [thread overview]
Message-ID: <20200212093654.4816-3-mgorman@techsingularity.net> (raw)
In-Reply-To: <20200212093654.4816-1-mgorman@techsingularity.net>
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Currently we loop through all threads of a core to evaluate if the core is
idle or not. This is unnecessary. If a thread of a core is not idle, skip
evaluating other threads of a core. Also while clearing the cpumask, bits
of all CPUs of a core can be cleared in one-shot.
Collecting ticks on a Power 9 SMT 8 system around select_idle_core
while running schbench shows us
(units are in ticks, hence lesser is better)
Without patch
N Min Max Median Avg Stddev
x 130 151 1083 284 322.72308 144.41494
With patch
N Min Max Median Avg Stddev Improvement
x 164 88 610 201 225.79268 106.78943 30.03%
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lkml.kernel.org/r/20191206172422.6578-1-srikar@linux.vnet.ibm.com
---
kernel/sched/fair.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 199d1476bb90..b058a9ceba7f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5787,10 +5787,12 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
bool idle = true;
for_each_cpu(cpu, cpu_smt_mask(core)) {
- __cpumask_clear_cpu(cpu, cpus);
- if (!available_idle_cpu(cpu))
+ if (!available_idle_cpu(cpu)) {
idle = false;
+ break;
+ }
}
+ cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
if (idle)
return core;
--
2.16.4
next prev parent reply other threads:[~2020-02-12 9:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-12 9:36 [RFC PATCH 00/11] Reconcile NUMA balancing decisions with the load balancer Mel Gorman
2020-02-12 9:36 ` [PATCH 01/11] sched/fair: Allow a small load imbalance between low utilisation SD_NUMA domains Mel Gorman
2020-02-12 9:36 ` Mel Gorman [this message]
2020-02-12 9:36 ` [PATCH 03/11] sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression Mel Gorman
2020-02-12 9:36 ` [PATCH 04/11] sched/numa: Trace when no candidate CPU was found on the preferred node Mel Gorman
2020-02-12 9:36 ` [PATCH 05/11] sched/numa: Distinguish between the different task_numa_migrate failure cases Mel Gorman
2020-02-12 14:43 ` Steven Rostedt
2020-02-12 15:59 ` Mel Gorman
2020-02-12 9:36 ` [PATCH 06/11] sched/numa: Prefer using an idle cpu as a migration target instead of comparing tasks Mel Gorman
2020-02-12 9:36 ` [PATCH 07/11] sched/numa: Find an alternative idle CPU if the CPU is part of an active NUMA balance Mel Gorman
2020-02-12 9:36 ` [PATCH 08/11] sched/numa: Bias swapping tasks based on their preferred node Mel Gorman
2020-02-13 10:31 ` Peter Zijlstra
2020-02-13 11:18 ` Mel Gorman
2020-02-12 13:22 ` [RFC PATCH 00/11] Reconcile NUMA balancing decisions with the load balancer Vincent Guittot
2020-02-12 14:07 ` Valentin Schneider
2020-02-12 15:48 ` Mel Gorman
2020-02-12 16:13 ` Vincent Guittot
2020-02-12 15:45 ` [PATCH 09/11] sched/fair: Split out helper to adjust imbalances between domains Mel Gorman
2020-02-12 15:46 ` [PATCH 10/11] sched/numa: Use similar logic to the load balancer for moving between domains with spare capacity Mel Gorman
2020-02-12 15:46 ` [PATCH 11/11] sched/numa: Use similar logic to the load balancer for moving between overloaded domains Mel Gorman
[not found] ` <20200214041232.18904-1-hdanton@sina.com>
2020-02-14 7:50 ` [PATCH 08/11] sched/numa: Bias swapping tasks based on their preferred node Mel Gorman
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