The patch titled
mm: add noaliencache boot option to disable numa alien caches
has been added to the -mm tree. Its filename is
add-noaliencache-boot-option-to-disable-numa-alien-caches.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: mm: add noaliencache boot option to disable numa alien caches
From: Paul Menage <menage@xxxxxxxxxx>
When using numa=fake on non-NUMA hardware there is no benefit to haveing the
alien caches, and they consume much memory.
Add a kernel boot option to disable them.
Cc: Christoph Lameter <clameter@xxxxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
Documentation/kernel-parameters.txt | 4 ++
mm/slab.c | 38 +++++++++++++++++++-------
2 files changed, 33 insertions(+), 9 deletions(-)
diff -puN mm/slab.c~add-noaliencache-boot-option-to-disable-numa-alien-caches mm/slab.c
--- a/mm/slab.c~add-noaliencache-boot-option-to-disable-numa-alien-caches
+++ a/mm/slab.c
@@ -869,6 +869,22 @@ static void __slab_error(const char *fun
dump_stack();
}
+/*
+ * By default on NUMA we use alien caches to stage the freeing of
+ * objects allocated from other nodes. This causes massive memory
+ * inefficiencies when using fake NUMA setup to split memory into a
+ * large number of small nodes, so it can be disabled on the command
+ * line
+ */
+
+static int use_alien_caches __read_mostly = 1;
+static int __init noaliencache_setup(char *s)
+{
+ use_alien_caches = 0;
+ return 1;
+}
+__setup("noaliencache", noaliencache_setup);
+
#ifdef CONFIG_NUMA
/*
* Special reaping functions for NUMA systems called from cache_reap().
@@ -1117,7 +1133,7 @@ static inline int cache_free_alien(struc
* Make sure we are not freeing a object from another node to the array
* cache on this cpu.
*/
- if (likely(slabp->nodeid == node))
+ if (likely(slabp->nodeid == node) || unlikely(!use_alien_caches))
return 0;
l3 = cachep->nodelists[node];
@@ -1195,7 +1211,7 @@ static int __cpuinit cpuup_callback(stru
list_for_each_entry(cachep, &cache_chain, next) {
struct array_cache *nc;
struct array_cache *shared;
- struct array_cache **alien;
+ struct array_cache **alien = NULL;
nc = alloc_arraycache(node, cachep->limit,
cachep->batchcount);
@@ -1207,9 +1223,11 @@ static int __cpuinit cpuup_callback(stru
if (!shared)
goto bad;
- alien = alloc_alien_cache(node, cachep->limit);
- if (!alien)
- goto bad;
+ if (use_alien_caches) {
+ alien = alloc_alien_cache(node, cachep->limit);
+ if (!alien)
+ goto bad;
+ }
cachep->array[cpu] = nc;
l3 = cachep->nodelists[node];
BUG_ON(!l3);
@@ -3593,13 +3611,15 @@ static int alloc_kmemlist(struct kmem_ca
int node;
struct kmem_list3 *l3;
struct array_cache *new_shared;
- struct array_cache **new_alien;
+ struct array_cache **new_alien = NULL;
for_each_online_node(node) {
- new_alien = alloc_alien_cache(node, cachep->limit);
- if (!new_alien)
- goto fail;
+ if (use_alien_caches) {
+ new_alien = alloc_alien_cache(node, cachep->limit);
+ if (!new_alien)
+ goto fail;
+ }
new_shared = alloc_arraycache(node,
cachep->shared*cachep->batchcount,
diff -puN Documentation/kernel-parameters.txt~add-noaliencache-boot-option-to-disable-numa-alien-caches Documentation/kernel-parameters.txt
--- a/Documentation/kernel-parameters.txt~add-noaliencache-boot-option-to-disable-numa-alien-caches
+++ a/Documentation/kernel-parameters.txt
@@ -1014,6 +1014,10 @@ and is between 256 and 4096 characters.
when set.
Format: <int>
+ noaliencache [MM, NUMA] Disables the allcoation of alien caches in
+ the slab allocator. Saves per-node memory, but will
+ impact performance on real NUMA hardware.
+
noalign [KNL,ARM]
noapic [SMP,APIC] Tells the kernel to not make use of any
_
Patches currently in -mm which might be from menage@xxxxxxxxxx are
add-noaliencache-boot-option-to-disable-numa-alien-caches.patch
-
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