From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [patch 2/4] Expose Power Management Policy option to users Date: Wed, 01 Aug 2007 03:02:55 +0900 Message-ID: <46AF794F.1020107@gmail.com> References: <20070705194909.337398431@intel.com> <20070705130518.135e4e3c.kristen.c.accardi@intel.com> <46AE12B6.6090408@garzik.org> <46AED656.8070407@gmail.com> <20070731093014.db9e0734.kristen.c.accardi@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from wa-out-1112.google.com ([209.85.146.181]:18261 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760314AbXGaSDD (ORCPT ); Tue, 31 Jul 2007 14:03:03 -0400 Received: by wa-out-1112.google.com with SMTP id v27so2166749wah for ; Tue, 31 Jul 2007 11:03:02 -0700 (PDT) In-Reply-To: <20070731093014.db9e0734.kristen.c.accardi@intel.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Kristen Carlson Accardi 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 Kristen Carlson Accardi wrote: > 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. I don't really care whose PS implementation goes in. Believe me. I try to stay away from that. I don't even like my previous implementation. ALPM has unnecessary performance penalty && is not applicable to non-ahci controller. Have you tested ALPM on non-intel ahcis? There are a lot out there these days. I don't think the interface you're suggesting is a good one. Do you? >> 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 wouldn't have used "might" if I had actual examples. Well, feel free to disregard anything following the "might". I just feel uneasy about jumping back and forth between PS and active states between consecutive commands. > 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. Is ALPM enabled by default? How do they deal with the performance degradation? -- tejun