Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 20 Oct 2001 04:50:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 20 Oct 2001 04:50:12 -0400 Received: from femail43.sdc1.sfba.home.com ([24.254.60.37]:43165 "EHLO femail43.sdc1.sfba.home.com") by vger.kernel.org with ESMTP id ; Sat, 20 Oct 2001 04:50:04 -0400 Content-Type: text/plain; charset=US-ASCII From: Rob Landley Reply-To: landley@trommello.org Organization: Boundaries Unlimited To: torvalds@transmeta.com (Linus Torvalds), linux-kernel@vger.kernel.org Subject: Re: Poor floppy performance in kernel 2.4.10 Date: Sat, 20 Oct 2001 00:20:38 -0400 X-Mailer: KMail [version 1.2] In-Reply-To: <20011018194415.S12055@athlon.random> <9qpihk$23p$1@penguin.transmeta.com> In-Reply-To: <9qpihk$23p$1@penguin.transmeta.com> MIME-Version: 1.0 Message-Id: <0110200020380L.15870@localhost.localdomain> Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Friday 19 October 2001 11:57, Linus Torvalds wrote: > Well, the original reason to not trust the media-change signal is that > some floppy drives simply do not implement the signal at all. Don't ask > me why. So a loong time ago Linux had the problem that when you changed > floppies you wouldn't see the new information - or you'd see _partially_ > new and old information depending on what your access patterns were and > what the caches contained. > > So it's pretty much across the board - broken SCSI, broken floppies, > just about any changeable media tends to have _some_ bad cases. And with > the floppy case, there was no way to notice at run-time whether the unit > was broken or not - the floppy drives have no ID's to blacklist etc. So > either you tell people to flush their caches by hand (which we did), or > you just always flush it between separate opens (which we later did). > > Linus The original dos case was timeout based. They sat down and changed the disk as fast as they could, and worked out it took something like two and a half seconds to swap disks. So if subsequent accesses were within two and a half seconds and got valid data on the first attempt, they decided it had to be the same disk... These days with the button it's probably more like a second and a half, but the principle's the same. Also, enough drives do it right (the vast majority), that a "broken_disk_change" module/boot option seems more sensible as a non-default thing for those that really are hosed... Rob - 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/