From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8) Date: Thu, 27 May 2010 19:26:33 +0100 Message-ID: <20100527182633.GN3543@srcf.ucam.org> References: <20100527003943.07c17f85@lxorguk.ukuu.org.uk> <20100527140655.GA28048@srcf.ucam.org> <20100527155201.GA31937@srcf.ucam.org> <20100527165931.GB1062@srcf.ucam.org> <20100527172343.GB2468@srcf.ucam.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from cavan.codon.org.uk ([93.93.128.6]:41882 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932542Ab0E0S0v (ORCPT ); Thu, 27 May 2010 14:26:51 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Thomas Gleixner Cc: Alan Cox , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Florian Mickler , Vitaly Wool , Peter Zijlstra , LKML , Paul@smtp1.linux-foundation.org, felipe.balbi@nokia.com, Linux OMAP Mailing List , Linux PM On Thu, May 27, 2010 at 07:59:02PM +0200, Thomas Gleixner wrote: > On Thu, 27 May 2010, Matthew Garrett wrote: > > ACPI provides no guarantees about what level of hardware functionality > > remains during S3. You don't have any useful ability to determine which > > events will generate wakeups. And from a purely practical point of view, > > since the latency is in the range of seconds, you'll never have a low > > enough wakeup rate to hit it. > > Right, it does not as of today. So we cannot use that on x86 > hardware. Fine. That does not prevent us to implement it for > architectures which can do it. And if x86 comes to the point where it > can handle it as well we're going to use it. Where is the problem ? If > x86 cannot guarantee the wakeup sources it's not going to be used for > such devices. The kernel just does not provide the service for it, so > what ? We were talking about PCs. Suspend-as-c-state is already implemented for OMAP. > So the only thing you are imposing to app writers is to use an > interface which solves nothing and does not save you any power at > all. It's already been demonstrated that the Android approach saves power. > Runnable tasks and QoS guarantees are the indicators whether you can > go to opportunistic suspend or not. Everything else is just window > dressing. As I keep saying, this is all much less interesting if you don't care about handling suboptimal applications. If you do care about them then the Android approach works. Nobody has demonstrated a scheduler-based one that does. -- Matthew Garrett | mjg59@srcf.ucam.org