MM: alloc_large_system_hash() can free some memory for non power-of-two bucketsize
authorEric Dumazet <dada1@cosmosbay.com>
Mon, 16 Jul 2007 06:38:05 +0000 (23:38 -0700)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>
Mon, 16 Jul 2007 16:05:35 +0000 (09:05 -0700)
commit1037b83bd04e31449dc9323f1e8ddada4264ef66
treeaad6be88185e675503847d3cf43a257ceb93d0f9
parentb92151bab91ef906378d3e0e7128d55dd641e966
MM: alloc_large_system_hash() can free some memory for non power-of-two bucketsize

alloc_large_system_hash() is called at boot time to allocate space for
several large hash tables.

Lately, TCP hash table was changed and its bucketsize is not a power-of-two
anymore.

On most setups, alloc_large_system_hash() allocates one big page (order >
0) with __get_free_pages(GFP_ATOMIC, order).  This single high_order page
has a power-of-two size, bigger than the needed size.

We can free all pages that wont be used by the hash table.

On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.

TCP established hash table entries: 32768 (order: 6, 393216 bytes)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/page_alloc.c