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authorJack Steiner <steiner@sgi.com>2010-05-26 14:42:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-27 09:12:44 -0700
commit6adef3ebe570bcde67fd6c16101451ddde5712b5 (patch)
tree0f60e2a4d01850ae33aee6cefc7a59845ede89a0 /mm
parent2c488db27b614816024e7994117f599337de0f34 (diff)
downloadkernel-6adef3ebe570bcde67fd6c16101451ddde5712b5.tar.gz
cpusets: new round-robin rotor for SLAB allocations
We have observed several workloads running on multi-node systems where memory is assigned unevenly across the nodes in the system. There are numerous reasons for this but one is the round-robin rotor in cpuset_mem_spread_node(). For example, a simple test that writes a multi-page file will allocate pages on nodes 0 2 4 6 ... Odd nodes are skipped. (Sometimes it allocates on odd nodes & skips even nodes). An example is shown below. The program "lfile" writes a file consisting of 10 pages. The program then mmaps the file & uses get_mempolicy(..., MPOL_F_NODE) to determine the nodes where the file pages were allocated. The output is shown below: # ./lfile allocated on nodes: 2 4 6 0 1 2 6 0 2 There is a single rotor that is used for allocating both file pages & slab pages. Writing the file allocates both a data page & a slab page (buffer_head). This advances the RR rotor 2 nodes for each page allocated. A quick confirmation seems to confirm this is the cause of the uneven allocation: # echo 0 >/dev/cpuset/memory_spread_slab # ./lfile allocated on nodes: 6 7 8 9 0 1 2 3 4 5 This patch introduces a second rotor that is used for slab allocations. Signed-off-by: Jack Steiner <steiner@sgi.com> Acked-by: Christoph Lameter <cl@linux-foundation.org> Cc: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Paul Menage <menage@google.com> Cc: Jack Steiner <steiner@sgi.com> Cc: Robin Holt <holt@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/slab.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/slab.c b/mm/slab.c
index 02786e1a32d2..8270ba3d1986 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3219,7 +3219,7 @@ static void *alternate_node_alloc(struct kmem_cache *cachep, gfp_t flags)
nid_alloc = nid_here = numa_node_id();
get_mems_allowed();
if (cpuset_do_slab_mem_spread() && (cachep->flags & SLAB_MEM_SPREAD))
- nid_alloc = cpuset_mem_spread_node();
+ nid_alloc = cpuset_slab_spread_node();
else if (current->mempolicy)
nid_alloc = slab_node(current->mempolicy);
put_mems_allowed();