Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261643AbVDZQLZ (ORCPT ); Tue, 26 Apr 2005 12:11:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261667AbVDZQLT (ORCPT ); Tue, 26 Apr 2005 12:11:19 -0400 Received: from colo.lackof.org ([198.49.126.79]:50139 "EHLO colo.lackof.org") by vger.kernel.org with ESMTP id S261643AbVDZQKg (ORCPT ); Tue, 26 Apr 2005 12:10:36 -0400 Date: Tue, 26 Apr 2005 10:12:59 -0600 From: Grant Grundler To: Benjamin Herrenschmidt Cc: Pavel Machek , Greg KH , Amit Gud , Alan Stern , Linux Kernel list , linux-pci@atrey.karlin.mff.cuni.cz, Andrew Morton , Jeff Garzik , cramerj@intel.com, USB development list Subject: Re: [PATCH] PCI: Add pci shutdown ability Message-ID: <20050426161259.GC2612@colo.lackof.org> References: <20050425182951.GA23209@kroah.com> <20050425185113.GC23209@kroah.com> <20050425190606.GA23763@kroah.com> <20050425204207.GA23724@elf.ucw.cz> <20050425205536.GF27771@neo.rr.com> <20050425210631.GE3906@elf.ucw.cz> <1114489812.7111.42.camel@gaston> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1114489812.7111.42.camel@gaston> X-Home-Page: http://www.parisc-linux.org/ User-Agent: Mutt/1.5.6+20040907i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1122 Lines: 26 On Tue, Apr 26, 2005 at 02:30:12PM +1000, Benjamin Herrenschmidt wrote: > Additionally, some machines won't properly park/flush the disk, it's > necessary to send the proper suspend commands to IDE hard disks prior to > shutting down or we risk data loss. That sounds like the disk is caching write data. SCSI has a "Write Cache Enable" bit in the "caching mode page". See "scsiinfo -c" output. 10 years ago I measured/compared performance of disabling WCE (plus queue depth of 8) and enabling WCE (queue depth 1). It's a wash for the workloads I was testing. I was told "stupid OSs" that didn't know about tagged queueing needed WCE for benchmarks. HP cared for exactly the same reasons: Bus Resets or Disk power failure would cause data loss with WCE enabled. Disabling WCE on current OSs would solve the above problem IFF IDE/SATA also supports "cache mode" page. grant - 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/