From: Richard Kennedy <richard@rsk.demon.co.uk>
Date: Wed, 10 Mar 2010 23:20:33 +0000 (-0800)
Subject: fs: buffer_head: remove kmem_cache constructor to reduce memory usage under slub
X-Git-Tag: v2.6.34-rc2~275
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=019b4d123aa7b9fc135b532e021cfde85db7665d;p=pandora-kernel.git

fs: buffer_head: remove kmem_cache constructor to reduce memory usage under slub

When using slub, having a kmem_cache constructor forces slub to add a free
pointer to the size of the cached object, which can have a significant
impact to the number of small objects that can fit into a slab.

As buffer_head is relatively small and we can have large numbers of them,
removing the constructor is a definite win.

On x86_64 removing the constructor gives me 39 objects/slab, 3 more than
without the patch.  And on x86_32 73 objects/slab, which is 9 more.

As alloc_buffer_head() already initializes each new object there is very
little difference in actual code run.

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <jens.axboe@oracle.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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