This is a note to let you know that I've just added the patch titled
mm, numa: really disable NUMA balancing by default on single node machines
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b0dc2b9bb4ab782115b964310518ee0b17784277 Mon Sep 17 00:00:00 2001
From: Mel Gorman <mgorman@xxxxxxx>
Date: Thu, 14 May 2015 15:17:09 -0700
Subject: mm, numa: really disable NUMA balancing by default on single node machines
From: Mel Gorman <mgorman@xxxxxxx>
commit b0dc2b9bb4ab782115b964310518ee0b17784277 upstream.
NUMA balancing is meant to be disabled by default on UMA machines but
the check is using nr_node_ids (highest node) instead of
num_online_nodes (online nodes).
The consequences are that a UMA machine with a node ID of 1 or higher
will enable NUMA balancing. This will incur useless overhead due to
minor faults with the impact depending on the workload. These are the
impact on the stats when running a kernel build on a single node machine
whose node ID happened to be 1:
vanilla patched
NUMA base PTE updates 5113158 0
NUMA huge PMD updates 643 0
NUMA page range updates 5442374 0
NUMA hint faults 2109622 0
NUMA hint local faults 2109622 0
NUMA hint local percent 100 100
NUMA pages migrated 0 0
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/mempolicy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2663,7 +2663,7 @@ static void __init check_numabalancing_e
if (numabalancing_override)
set_numabalancing_state(numabalancing_override == 1);
- if (nr_node_ids > 1 && !numabalancing_override) {
+ if (num_online_nodes() > 1 && !numabalancing_override) {
pr_info("%s automatic NUMA balancing. "
"Configure with numa_balancing= or the "
"kernel.numa_balancing sysctl",
Patches currently in stable-queue which might be from mgorman@xxxxxxx are
queue-3.14/mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch
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