From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753070AbYIHOW0 (ORCPT ); Mon, 8 Sep 2008 10:22:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751811AbYIHOWR (ORCPT ); Mon, 8 Sep 2008 10:22:17 -0400 Received: from casper.infradead.org ([85.118.1.10]:55519 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751676AbYIHOWQ (ORCPT ); Mon, 8 Sep 2008 10:22:16 -0400 Date: Mon, 8 Sep 2008 07:22:20 -0700 From: Arjan van de Ven To: Pavel Machek Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, dwmw2@infradead.org, drepper@redhat.com, mingo@elte.hu, tglx@tglx.de Subject: Re: [PATCH 12/13] hrtimer: create a "timer_slack" field in the task struct Message-ID: <20080908072220.75fc3dfd@infradead.org> In-Reply-To: <20080908141555.GB31784@elf.ucw.cz> References: <20080901160343.75a89ec9@infradead.org> <20080901161423.59ebf2fc@infradead.org> <20080902100439.GA11383@elf.ucw.cz> <20080902060323.70245b83@infradead.org> <20080908132713.GA18486@elf.ucw.cz> <20080908064002.7abc2a22@infradead.org> <20080908141555.GB31784@elf.ucw.cz> Organization: Intel X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.11; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 8 Sep 2008 16:15:55 +0200 Pavel Machek wrote: > On Mon 2008-09-08 06:40:02, Arjan van de Ven wrote: > > On Mon, 8 Sep 2008 15:27:16 +0200 > > Pavel Machek wrote: > > > > > > > > ... which nobody uses today. > > > > It's not just new syscalls, it's a new glibc api as well at that > > > > point. > > > > > > ...and new applications, yes. I believe applications should > > > explicitely enable slacking timers. > > > > timers are slacking today, at least for select() and poll(), and > > are a great deal more so than the defaults in this patchkit. > > Ok, so select()/poll() may default to non-zero slack for legacy apps. that's whats there > > > The great advantage of the prctl() approach (which is usable) over > > new system calls and glibc APIs is that it will get used, because > > the admin can use it just like he uses the "nice" command, on > > existing software. > > Yes, it is a great advantage, but it feels like a hack. Maybe it is > better done with LD_PRELOAD or something? that's not working very well in general, and doesn't work across exec etc. > > I'd certianly want the applications to specify slack themselves in > like 10 years. We've been talking to Ulrich to figure out what the right API for this is (eg how to extend select/poll for this) and I still plan to work on this, but both Linus and Ulrich seem to be very ademant that it means only few apps will use it (and I agree with that, just look at how many apps use linux specific APIs such as sendfile(), linux AIO etc... ) -- If you want to reach me at my work email, use arjan@linux.intel.com For development, discussion and tips for power savings, visit http://www.lesswatts.org