From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754574AbYHJUDP (ORCPT ); Sun, 10 Aug 2008 16:03:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754353AbYHJUCz (ORCPT ); Sun, 10 Aug 2008 16:02:55 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:3672 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754347AbYHJUCz (ORCPT ); Sun, 10 Aug 2008 16:02:55 -0400 Date: Sat, 9 Aug 2008 14:54:47 +0200 From: Pavel Machek To: "Pallipadi, Venkatesh" Cc: David Woodhouse , "linux-kernel@vger.kernel.org" , Thomas Gleixner , Ingo Molnar , "arjan@infradead.org" Subject: Re: [RFC] Imprecise timers. Message-ID: <20080809125447.GA13169@ucw.cz> References: <1216695757.18980.16.camel@shinybook.infradead.org> <7E82351C108FA840AB1866AC776AEC4608E23BE7@orsmsx505.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7E82351C108FA840AB1866AC776AEC4608E23BE7@orsmsx505.amr.corp.intel.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 2008-07-28 17:36:57, Pallipadi, Venkatesh wrote: > > > >-----Original Message----- > >From: linux-kernel-owner@vger.kernel.org > >[mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of David > >Woodhouse > >Sent: Monday, July 21, 2008 8:03 PM > >To: linux-kernel@vger.kernel.org > >Cc: Thomas Gleixner; Ingo Molnar; arjan@infradead.org > >Subject: [RFC] Imprecise timers. > > > >Many users of timers don't really care too much about exactly > >when their > >timer fires -- and waking a CPU to satisfy such a timer is a waste of > >power. This patch implements a 'range' timer which will fire > >at a 'convenient' > >moment within given constraints. > > > >It's implemented by a deferrable timer at the beginning of the range, > >which will run some time later when the CPU happens to be awake. And a > >non-deferrable timer at the hard deadline, to ensure it really does > >happen by then. > > > > One concern I have is drivers using range_timers thinking that they need > some upper bound, while all they need is a simple deferrable timer. With that > we will have multiple timers waking up the CPU all the time (say, on > different CPUs) problem again. Even without the timers waking up all I don't get it. Who has timers that can be deferred forever? At that point they may simply not set the timer at all, right? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html