From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Steigerwald Subject: Re: Large buffer cache in EXT4 Date: Mon, 18 Feb 2013 14:16:24 +0100 Message-ID: <201302181416.24599.Martin@lichtvoll.de> References: <201302171125.40116.Martin@lichtvoll.de> <20130218043517.GB10361@thunk.org> (sfid-20130218_094303_618638_F73771F3) Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Subranshu Patel , linux-ext4@vger.kernel.org To: "Theodore Ts'o" Return-path: Received: from mondschein.lichtvoll.de ([194.150.191.11]:34150 "EHLO mail.lichtvoll.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754228Ab3BRNQ2 convert rfc822-to-8bit (ORCPT ); Mon, 18 Feb 2013 08:16:28 -0500 In-Reply-To: <20130218043517.GB10361@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: Am Montag, 18. Februar 2013 schrieb Theodore Ts'o: > On Sun, Feb 17, 2013 at 11:25:39AM +0100, Martin Steigerwald wrote: > > What I never really understand was what is the clear distinction > > between dirty pages and disk block buffers. Why isn=B4t anything th= at is > > about to be written to disk in one cache? >=20 > The buffer cache is indexed by physical block number, and each buffer > in the buffer cache is the size of the block size used for I/O to the > device. >=20 > The page cache is indexed by , and each pag= e > is the size of a VM page (i.e.4k for x86 systems, 16k for Power > systems, etc.) >=20 > Certain file systems, including ext3, ext4, and ocfs2, use the jbd or > jbd2 layer to handle their physical block journalling, and this layer > fundamentally uses the buffer cache, since it is concerned with > controlling when specific file system blocks are allowed to ben > written back to the hard drive. Thank you for the explanation, Ted. --=20 Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html