Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753930AbZGTNsq (ORCPT ); Mon, 20 Jul 2009 09:48:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753723AbZGTNso (ORCPT ); Mon, 20 Jul 2009 09:48:44 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:32824 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753688AbZGTNso (ORCPT ); Mon, 20 Jul 2009 09:48:44 -0400 Subject: Re: [RFC][PATCH] Introduce CLOCK_REALTIME_COARSE From: Peter Zijlstra To: Arjan van de Ven Cc: john stultz , Thomas Gleixner , lkml , Thomas Gleixner , Ingo Molnar , Andi Kleen , nikolag@ca.ibm.com, Darren Hart In-Reply-To: <20090720063305.2ad49d40@infradead.org> References: <1247873945.8334.67.camel@localhost.localdomain> <1247954978.14494.19.camel@work-vm> <20090718153011.1de3af8e@infradead.org> <1248088622.15751.8465.camel@twins> <20090720063305.2ad49d40@infradead.org> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Mon, 20 Jul 2009 15:49:14 +0200 Message-Id: <1248097754.15751.8867.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1235 Lines: 31 On Mon, 2009-07-20 at 06:33 -0700, Arjan van de Ven wrote: > > Maybe power64, sparc64 and s390x qualify, but certainly nothing on x86 > > does. > > the x86 on my desk disagrees. >From what I know even nehalem doesn't have fully synced tscs when your machine is large enough, and the timers are still a tad expensive. Maybe your desktop is next-gen? 't would be nice to finally have an x86 that has usable clock and timer hardware. I'm sure tglx would be pleasantly surprised :-) > > Furthermore, on the software side we'd need a few modifications, such > > as doing lazy accounting for things like u/s-time which currently > > rely on the tick and moving the load-balancing into a hrtimer. > > I thought the load balancer no longer runs as a timer.. but I could > well be wrong. It doesn't but it does need wakeup kicks, which are currently done from the tick. And I'm not at all disagreeing that we want the tick gone, I'm just pointing out there's some challenges ahead still ;-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/