From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765327AbXGaQdW (ORCPT ); Tue, 31 Jul 2007 12:33:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757185AbXGaQdL (ORCPT ); Tue, 31 Jul 2007 12:33:11 -0400 Received: from mga02.intel.com ([134.134.136.20]:47088 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757722AbXGaQdJ (ORCPT ); Tue, 31 Jul 2007 12:33:09 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.19,204,1183359600"; d="scan'208";a="272724235" Date: Tue, 31 Jul 2007 09:30:14 -0700 From: Kristen Carlson Accardi To: Tejun Heo Cc: Jeff Garzik , James.Bottomley@steeleye.com, linux-scsi@vger.kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, edwintorok@gmail.com, axboe@kernel.dk Subject: Re: [patch 2/4] Expose Power Management Policy option to users Message-Id: <20070731093014.db9e0734.kristen.c.accardi@intel.com> In-Reply-To: <46AED656.8070407@gmail.com> References: <20070705194909.337398431@intel.com> <20070705130518.135e4e3c.kristen.c.accardi@intel.com> <46AE12B6.6090408@garzik.org> <46AED656.8070407@gmail.com> X-Mailer: Sylpheed 2.3.1 (GTK+ 2.10.13; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 31 Jul 2007 15:27:34 +0900 Tejun Heo wrote: > Jeff Garzik wrote: > > Any chance the SCSI peeps could ACK this, and then let me include it in > > the ALPM patchset in the libata tree? > > ATA link PS is pretty complex with HIPM, DIPM and AHCI ALPM. I'm not > sure whether this three level knob would be sufficient. It might be > good enough if we're gonna develop extensive in-kernel black/white list > specifying which method works on which combination but my gut tells me > that it's best left to userland (probably in the form of per-notebook PS > profile). I think what you are saying is that you'd like a way to use your HIPM and DIPM without ALPM on the AHCI driver. Fine - it's really easy to add these levels later - if they don't make sense at the sysfs interface we can add module params to specify the definition of "min_power" as being performed via HIPM and DIPM instead of ALPM - although as of yet we have no evidence what so ever that this method actually adds value over ALPM. > > Adding to the fun, there are quite a few broken devices out there which > act weirdly when link PS actions are taken. OK - this is why I added the blacklist for this feature. > > Also, I generally don't think AHCI ALPM is a good idea. It doesn't have > 'cool down' period before entering PS state which unnecessarily hampers > performance and might increase chance of device malfunction. "might increase"? How about some actual examples of where you've shown this to be a problem? I can assert that I think ALPM is a good idea, because I've never had a report of it causing problems. Windows has been using this feature for a very long time - and you have to admit that they have a pretty large market share. Nobody is complaining about ALPM increasing device malfunction, so unless you have proof it seems insane to nak due to this.