From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 23 May 2001 18:10:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 23 May 2001 18:09:55 -0400 Received: from penguin.e-mind.com ([195.223.140.120]:7448 "EHLO penguin.e-mind.com") by vger.kernel.org with ESMTP id ; Wed, 23 May 2001 18:09:46 -0400 Date: Thu, 24 May 2001 00:09:33 +0200 From: Andrea Arcangeli To: Linus Torvalds Cc: "Stephen C. Tweedie" , linux-kernel@vger.kernel.org Subject: Re: DVD blockdevice buffers Message-ID: <20010524000933.A764@athlon.random> In-Reply-To: <20010523205748.L8080@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ; from torvalds@transmeta.com on Wed, May 23, 2001 at 01:01:56PM -0700 X-GnuPG-Key-URL: http://e-mind.com/~andrea/aa.gnupg.asc X-PGP-Key-URL: http://e-mind.com/~andrea/aa.asc Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 23, 2001 at 01:01:56PM -0700, Linus Torvalds wrote: > [..] I assume that Andrea basically > made the block-size be the same as the page size. That's how I would have exactly (softblocksize is 4k fixed, regardless of the page cache size to avoid confusing device drivers). > done it (and then waited for people to find real life cases where we want > to allow sector writes). Correct, the partial write logic is kind of disabled on x86 because the artificial softblocksize of the blkdev pagecache matches the pagecachesize but it should just work on the other archs. Now I can try to make the bh more granular for partial writes in a dynamic manner (so we don't pay the overhead of the 512byte bh in the common case) but I think this would need its own additional logic and I prefer to think about it after I solved the coherency issues between pinned buffer cache and filesystem, so after the showstoppers are solved and the patch is just usable in real life (possibly with the overhead of read-modify-write for some workload doing small random write I/O). An easy short term fix for removing the read-modify-write would be to use the hardblocksize of the underlying device as the softblocksize but again that would cause us to pay for the 512byte bhs which I don't like to... ;) Andrea