Commit c2fdf3a9 authored by Anton Blanchard's avatar Anton Blanchard Committed by Linus Torvalds

mm: enable hashdist by default on 64bit NUMA

On PowerPC we allocate large boot time hashes on node 0.  This leads to an
imbalance in the free memory, for example on a 64GB box (4 x 16GB nodes):

Free memory:
Node 0: 97.03%
Node 1: 98.54%
Node 2: 98.42%
Node 3: 98.53%

If we switch to using vmalloc (like ia64 and x86-64) things are more
balanced:

Free memory:
Node 0: 97.53%
Node 1: 98.35%
Node 2: 98.33%
Node 3: 98.33%

For many HPC applications we are limited by the free available memory on
the smallest node, so even though the same amount of memory is used the
better balancing helps.

Since all 64bit NUMA capable architectures should have sufficient vmalloc
space, it makes sense to enable it via CONFIG_64BIT.
Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
Acked-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: default avatarRalf Baechle <ralf@linux-mips.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 704503d8
......@@ -146,10 +146,10 @@ extern void *alloc_large_system_hash(const char *tablename,
#define HASH_EARLY 0x00000001 /* Allocating during early boot? */
/* Only NUMA needs hash distribution.
* IA64 and x86_64 have sufficient vmalloc space.
/* Only NUMA needs hash distribution. 64bit NUMA architectures have
* sufficient vmalloc space.
*/
#if defined(CONFIG_NUMA) && (defined(CONFIG_IA64) || defined(CONFIG_X86_64))
#if defined(CONFIG_NUMA) && defined(CONFIG_64BIT)
#define HASHDIST_DEFAULT 1
#else
#define HASHDIST_DEFAULT 0
......
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