Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753924AbZGVVkx (ORCPT ); Wed, 22 Jul 2009 17:40:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753761AbZGVVkx (ORCPT ); Wed, 22 Jul 2009 17:40:53 -0400 Received: from slow3-v.mail.gandi.net ([217.70.178.89]:43088 "EHLO slow3-v.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753725AbZGVVkw (ORCPT ); Wed, 22 Jul 2009 17:40:52 -0400 Date: Wed, 22 Jul 2009 14:39:46 -0700 From: Josh Triplett To: Peter Zijlstra Cc: Arjan van de Ven , john stultz , Thomas Gleixner , lkml , Thomas Gleixner , Ingo Molnar , Andi Kleen , nikolag@ca.ibm.com, Darren Hart Subject: Re: [RFC][PATCH] Introduce CLOCK_REALTIME_COARSE Message-ID: <20090722213942.GA4337@josh-work.beaverton.ibm.com> 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> <1248097754.15751.8867.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1248097754.15751.8867.camel@twins> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1133 Lines: 27 On Mon, Jul 20, 2009 at 03:49:14PM +0200, Peter Zijlstra wrote: > 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. All single-socket Nehalem boards have synced TSCs, and some multi-socket Nehalem boards have synced TSCs, notably Intel's. I don't know if you can safely rely on the latter, though. > Maybe your desktop is next-gen? 't would be nice to finally have an x86 > that has usable clock and timer hardware. x86 CPUs with the ARAT feature ("always running APIC timer") will let you use the local APIC even in deep C-states. I don't know about the overhead of the local APIC. - Josh Triplett -- 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/