Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756553Ab0FCPoK (ORCPT ); Thu, 3 Jun 2010 11:44:10 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:63712 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756126Ab0FCPoH convert rfc822-to-8bit (ORCPT ); Thu, 3 Jun 2010 11:44:07 -0400 MIME-Version: 1.0 Message-ID: <6e97a82a-c754-493e-bbf5-58f0bb6a18b5@default> Date: Thu, 3 Jun 2010 08:43:05 -0700 (PDT) From: Dan Magenheimer To: ngupta@vflare.org, andreas.dilger@oracle.com Cc: Minchan Kim , chris.mason@oracle.com, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, adilger@sun.com, tytso@mit.edu, mfasheh@suse.com, joel.becker@oracle.com, matthew@wil.cx, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, ocfs2-devel@oss.oracle.com, linux-mm@kvack.org, jeremy@goop.org, JBeulich@novell.com, kurt.hackel@oracle.com, npiggin@suse.de, dave.mccracken@oracle.com, riel@redhat.com, avi@redhat.com, konrad.wilk@oracle.com Subject: RE: [PATCH V2 0/7] Cleancache (was Transcendent Memory): overview References: <20100528173510.GA12166%ca-server1.us.oracle.comAANLkTilV-4_QaNq5O0WSplDx1Oq7JvkgVrEiR1rgf1up@mail.gmail.com> <489aa002-6d42-4dd5-bb66-81c665f8cdd1@default> <4C07179F.5080106@vflare.org> <3721BEE2-DF2D-452A-8F01-E690E32C6B33@oracle.com 4C074ACE.9020704@vflare.org> In-Reply-To: <4C074ACE.9020704@vflare.org> X-Priority: 3 X-Mailer: Oracle Beehive Extensions for Outlook 1.5.1.5.2 (401224) [OL 12.0.6514.5000] Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT X-Auth-Type: Internal IP X-Source-IP: rcsinet13.oracle.com [148.87.113.125] X-CT-RefId: str=0001.0A090207.4C07CDAA.017F:SCFMA4539811,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1085 Lines: 22 > On 06/03/2010 10:23 AM, Andreas Dilger wrote: > > On 2010-06-02, at 20:46, Nitin Gupta wrote: > > > I was thinking it would be quite clever to do compression in, say, > > 64kB or 128kB chunks in a mapping (to get decent compression) and > > then write these compressed chunks directly from the page cache > > to disk in btrfs and/or a revived compressed ext4. > > Batching of pages to get good compression ratio seems doable. Is there evidence that batching a set of random individual 4K pages will have a significantly better compression ratio than compressing the pages separately? I certainly understand that if the pages are from the same file, compression is likely to be better, but pages evicted from the page cache (which is the source for all cleancache_puts) are likely to be quite a bit more random than that, aren't they? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/