From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel Subject: Re: [PATCH] fs: buffer_head, remove kmem_cache constructor to reduce memory usage under slub Date: Tue, 09 Feb 2010 11:48:20 -0500 Message-ID: <4B7191D4.4000101@redhat.com> References: <1265722191.4033.36.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Alexander Viro , Andrew Morton , linux-fsdevel , lkml , Jens Axboe , Nick Piggin , "Theodore Ts'o" To: Richard Kennedy Return-path: Received: from mx1.redhat.com ([209.132.183.28]:54938 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754411Ab0BIQtH (ORCPT ); Tue, 9 Feb 2010 11:49:07 -0500 In-Reply-To: <1265722191.4033.36.camel@localhost> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 02/09/2010 08:29 AM, Richard Kennedy wrote: > fs: Remove the buffer_head 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 Reviewed-by: Rik van Riel -- All rights reversed.