[PATCH 4/9] cpumask: improve on cpumask_local_spread() locality

From: Yury Norov <yury.norov@gmail.com>
To: linux-kernel@vger.kernel.org,
	"David S. Miller" <davem@davemloft.net>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Barry Song <baohua@kernel.org>, Ben Segall <bsegall@google.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Gal Pressman <gal@nvidia.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Haniel Bristot de Oliveira <bristot@redhat.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Ingo Molnar <mingo@redhat.com>,
	Jacob Keller <jacob.e.keller@intel.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Jason Gunthorpe <jgg@nvidia.com>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Leon Romanovsky <leonro@nvidia.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Mel Gorman <mgorman@suse.de>, Peter Lafreniere <peter@n8pjl.ca>,
	Peter Zijlstra <peterz@infradead.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Saeed Mahameed <saeedm@nvidia.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Tariq Toukan <tariqt@nvidia.com>,
	Tariq Toukan <ttoukan.linux@gmail.com>,
	Tony Luck <tony.luck@intel.com>,
	Valentin Schneider <vschneid@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>
Cc: Yury Norov <yury.norov@gmail.com>,
	linux-crypto@vger.kernel.org, netdev@vger.kernel.org,
	linux-rdma@vger.kernel.org
Subject: [PATCH 4/9] cpumask: improve on cpumask_local_spread() locality
Date: Fri, 20 Jan 2023 20:24:31 -0800	[thread overview]
Message-ID: <20230121042436.2661843-5-yury.norov@gmail.com> (raw)
In-Reply-To: <20230121042436.2661843-1-yury.norov@gmail.com>

Switch cpumask_local_spread() to use newly added sched_numa_find_nth_cpu(),
which takes into account distances to each node in the system.

For the following NUMA configuration:

root@debian:~# numactl -H
available: 4 nodes (0-3)
node 0 cpus: 0 1 2 3
node 0 size: 3869 MB
node 0 free: 3740 MB
node 1 cpus: 4 5
node 1 size: 1969 MB
node 1 free: 1937 MB
node 2 cpus: 6 7
node 2 size: 1967 MB
node 2 free: 1873 MB
node 3 cpus: 8 9 10 11 12 13 14 15
node 3 size: 7842 MB
node 3 free: 7723 MB
node distances:
node   0   1   2   3
  0:  10  50  30  70
  1:  50  10  70  30
  2:  30  70  10  50
  3:  70  30  50  10

The new cpumask_local_spread() traverses cpus for each node like this:

node 0:   0   1   2   3   6   7   4   5   8   9  10  11  12  13  14  15
node 1:   4   5   8   9  10  11  12  13  14  15   0   1   2   3   6   7
node 2:   6   7   0   1   2   3   8   9  10  11  12  13  14  15   4   5
node 3:   8   9  10  11  12  13  14  15   4   5   6   7   0   1   2   3

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Acked-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Peter Lafreniere <peter@n8pjl.ca>
---
 lib/cpumask.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/lib/cpumask.c b/lib/cpumask.c
index c7c392514fd3..255974cd6734 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -110,7 +110,7 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask)
 #endif
 
 /**
- * cpumask_local_spread - select the i'th cpu with local numa cpu's first
+ * cpumask_local_spread - select the i'th cpu based on NUMA distances
  * @i: index number
  * @node: local numa_node
  *
@@ -132,15 +132,7 @@ unsigned int cpumask_local_spread(unsigned int i, int node)
 		if (cpu < nr_cpu_ids)
 			return cpu;
 	} else {
-		/* NUMA first. */
-		cpu = cpumask_nth_and(i, cpu_online_mask, cpumask_of_node(node));
-		if (cpu < nr_cpu_ids)
-			return cpu;
-
-		i -= cpumask_weight_and(cpu_online_mask, cpumask_of_node(node));
-
-		/* Skip NUMA nodes, done above. */
-		cpu = cpumask_nth_andnot(i, cpu_online_mask, cpumask_of_node(node));
+		cpu = sched_numa_find_nth_cpu(cpu_online_mask, i, node);
 		if (cpu < nr_cpu_ids)
 			return cpu;
 	}
-- 
2.34.1

