+ mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch added to -mm tree

+ mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm, numa: really disable NUMA balancing by default on single node machines
has been added to the -mm tree.  Its filename is
     mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch

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------------------------------------------------------
From: Mel Gorman <mgorman@suse.de>
Subject: mm, numa: really disable NUMA balancing by default on single node machines

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@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org>	[3.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mempolicy.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN mm/mempolicy.c~mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines mm/mempolicy.c
--- a/mm/mempolicy.c~mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines
+++ a/mm/mempolicy.c
@@ -2518,7 +2518,7 @@ 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 -mm which might be from mgorman@suse.de are

mm-numa-really-disable-numa-balancing-by-default-on-single-node-machines.patch
jbd2-revert-must-not-fail-allocation-loops-back-to-gfp_nofail.patch
thp-cleanup-how-khugepaged-enters-freezer.patch
mm-new-mm-hook-framework.patch
mm-new-arch_remap-hook.patch
powerpc-mm-tracking-vdso-remap.patch
memblock-introduce-a-for_each_reserved_mem_region-iterator.patch
mm-meminit-move-page-initialization-into-a-separate-function.patch
mm-meminit-only-set-page-reserved-in-the-memblock-region.patch
mm-page_alloc-pass-pfn-to-__free_pages_bootmem.patch
mm-page_alloc-pass-pfn-to-__free_pages_bootmem-fix.patch
mm-meminit-make-__early_pfn_to_nid-smp-safe-and-introduce-meminit_pfn_in_nid.patch
mm-meminit-inline-some-helper-functions.patch
mm-meminit-inline-some-helper-functions-fix.patch
mm-meminit-inline-some-helper-functions-fix2.patch
mm-meminit-initialise-a-subset-of-struct-pages-if-config_deferred_struct_page_init-is-set.patch
mm-meminit-initialise-a-subset-of-struct-pages-if-config_deferred_struct_page_init-is-set-fix.patch
mm-meminit-initialise-remaining-struct-pages-in-parallel-with-kswapd.patch
mm-meminit-minimise-number-of-pfn-page-lookups-during-initialisation.patch
x86-mm-enable-deferred-struct-page-initialisation-on-x86-64.patch
mm-meminit-free-pages-in-large-chunks-where-possible.patch
mm-meminit-reduce-number-of-times-pageblocks-are-set-during-struct-page-init.patch
mm-meminit-reduce-number-of-times-pageblocks-are-set-during-struct-page-init-fix.patch
mm-meminit-remove-mminit_verify_page_links.patch
mm-meminit-finish-initialisation-of-struct-pages-before-basic-setup.patch
mm-meminit-finish-initialisation-of-struct-pages-before-basic-setup-fix.patch
mm-vmscan-do-not-throttle-based-on-pfmemalloc-reserves-if-node-has-no-reclaimable-pages.patch
page-flags-trivial-cleanup-for-pagetrans-helpers.patch
page-flags-introduce-page-flags-policies-wrt-compound-pages.patch
page-flags-define-pg_locked-behavior-on-compound-pages.patch
page-flags-define-behavior-of-fs-io-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-lru-related-flags-on-compound-pages.patch
page-flags-define-behavior-slb-related-flags-on-compound-pages.patch
page-flags-define-behavior-of-xen-related-flags-on-compound-pages.patch
page-flags-define-pg_reserved-behavior-on-compound-pages.patch
page-flags-define-pg_swapbacked-behavior-on-compound-pages.patch
page-flags-define-pg_swapcache-behavior-on-compound-pages.patch
page-flags-define-pg_mlocked-behavior-on-compound-pages.patch
page-flags-define-pg_uncached-behavior-on-compound-pages.patch
page-flags-define-pg_uptodate-behavior-on-compound-pages.patch
page-flags-look-on-head-page-if-the-flag-is-encoded-in-page-mapping.patch
mm-sanitize-page-mapping-for-tail-pages.patch
mm-vmscan-fix-the-page-state-calculation-in-too_many_isolated.patch
mm-move-lazy-free-pages-to-inactive-list.patch
mm-move-lazy-free-pages-to-inactive-list-fix.patch
mm-move-lazy-free-pages-to-inactive-list-fix-fix.patch
linux-next.patch
do_shared_fault-check-that-mmap_sem-is-held.patch