Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754024Ab1DDI0H (ORCPT ); Mon, 4 Apr 2011 04:26:07 -0400 Received: from service87.mimecast.com ([94.185.240.25]:32768 "HELO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753848Ab1DDI0E convert rfc822-to-8bit (ORCPT ); Mon, 4 Apr 2011 04:26:04 -0400 Subject: Re: [GIT PULL] omap changes for v2.6.39 merge window From: Marc Zyngier To: Arnd Bergmann Cc: Russell King - ARM Linux , david@lang.hm, Nicolas Pitre , Tony Lindgren , Catalin Marinas , lkml , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, "H. Peter Anvin" , Ingo Molnar , linux-omap@vger.kernel.org, Linus Torvalds , David Brown , Detlef Vollmann In-Reply-To: <201104040259.26601.arnd@arndb.de> References: <201104031726.37420.arnd@arndb.de> <20110403160324.GA8050@n2100.arm.linux.org.uk> <201104040259.26601.arnd@arndb.de> Organization: ARM Ltd Date: Mon, 04 Apr 2011 09:26:19 +0100 Message-ID: <1301905579.417.16.camel@e102391-lin.cambridge.arm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 X-OriginalArrivalTime: 04 Apr 2011 08:25:52.0996 (UTC) FILETIME=[E96B2240:01CBF2A1] X-MC-Unique: 111040409255707201 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1290 Lines: 31 On Mon, 2011-04-04 at 02:59 +0200, Arnd Bergmann wrote: > Abstracting sched_clock() to be run-time selected is something that > needs to be taken care of. Maybe we could have a generic sched_clock > implementation that is written on top of clocksource instead of jiffies, > and always select that on architectures that have a decent clocksource. > Are there any platforms on ARM where that would be a bad idea? I believe > the main reaons why they are separate is that on x86 you can use the TSC > for sched_clock in many cases where you cannot use it for clocksource. I've proposed a mechanism for a run-time selectable sched_clock() implementation as part of my A15 timer patch set: http://www.spinics.net/lists/arm-kernel/msg116891.html and more specifically patches #10 and #11. I'm not completely pleased with it (the fact that it embeds a copy of the generic sched_clock() to be used as a default is properly ugly), but maybe this could be used as a base for further discussion. Cheers, M. -- Reality is an implementation detail. -- 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/