Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754782AbYCBKP1 (ORCPT ); Sun, 2 Mar 2008 05:15:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753203AbYCBKPP (ORCPT ); Sun, 2 Mar 2008 05:15:15 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:2465 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753025AbYCBKPN (ORCPT ); Sun, 2 Mar 2008 05:15:13 -0500 Date: Sun, 24 Feb 2008 19:03:39 +0100 From: Pavel Machek To: Alan Cox Cc: Elias Oltmanns , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, Jens Axboe Subject: Re: [RFC] Disk shock protection (revisited) Message-ID: <20080224180339.GA3861@ucw.cz> References: <87skzgd1zk.fsf@denkblock.local> <20080226123946.75dbe3d2@core> <87mypl8p49.fsf@denkblock.local> <20080228111349.6831925c@core> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080228111349.6831925c@core> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1588 Lines: 38 Hi! > > > That sounds like a non starter. What if the box is busy, what if the > > > daemon or something you touch needs memory and causes paging ? > > > > The daemon runs mlock'd anyway, so there won't be any need for paging > > mlock does not guarantee anything of that form. A syscall by an mlocked > process which causes a memory allocation can cause paging of another > process on the system. Well... but you can be careful about the syscalls, right? Anyway, active protection is 'best effort' anyway. There's not enough time to park heads if you drop the machine without tilting it first... and we have been running with no protection for years now... > > stays in memory all the time, it can go ahead and notify the kernel that > > the disk heads should be unloaded. The kernel takes care to insert the > > idle immediate command at the head of the queue. Am I missing something? > > Yes - the fact we may well have bounced off the floor already. Well, shit happens. Even notebook with parked harddrive is not guaranteed to survive the fall. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/