Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932673Ab2JZMjV (ORCPT ); Fri, 26 Oct 2012 08:39:21 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:33340 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932607Ab2JZMjU (ORCPT ); Fri, 26 Oct 2012 08:39:20 -0400 X-Authority-Analysis: v=2.0 cv=YP4dOG6x c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=rDHpwsyNOsUA:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=meVymXHHAAAA:8 a=HXw8KzeH-oIA:10 a=i2TgY9j9Z3Rknev0DCwA:9 a=PUjeQqilurYA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.115.198 Message-ID: <1351255155.8467.55.camel@gandalf.local.home> Subject: Re: [PATCH 01/16] math128: Introduce various 128bit primitives From: Steven Rostedt To: Thomas Gleixner Cc: Peter Zijlstra , Ingo Molnar , Linus Torvalds , Juri Lelli , mingo@redhat.com, oleg@redhat.com, fweisbec@gmail.com, darren@dvhart.com, johan.eker@ericsson.com, p.faure@akatech.ch, linux-kernel@vger.kernel.org, claudio@evidence.eu.com, michael@amarulasolutions.com, fchecconi@gmail.com, tommaso.cucinotta@sssup.it, nicola.manica@disi.unitn.it, luca.abeni@unitn.it, dhaval.giani@gmail.com, hgu1972@gmail.com, paulmck@linux.vnet.ibm.com, raistlin@linux.it, insop.song@ericsson.com, liming.wang@windriver.com, jkacur@redhat.com, harald.gustafsson@ericsson.com, vincent.guittot@linaro.org, Andrew Morton Date: Fri, 26 Oct 2012 08:39:15 -0400 In-Reply-To: References: <1351115634-8420-1-git-send-email-juri.lelli@gmail.com> <1351115634-8420-2-git-send-email-juri.lelli@gmail.com> <1351172849.12171.10.camel@twins> <1351241389.12171.45.camel@twins> <20121026092421.GB628@gmail.com> <1351244130.16863.7.camel@twins> <20121026094207.GA2179@gmail.com> <1351245264.16863.12.camel@twins> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.4.3-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1212 Lines: 28 On Fri, 2012-10-26 at 12:36 +0200, Thomas Gleixner wrote: > By all means. nsec precision is a completly academic thought > exercise. It's really pointless to even think about anything below > microseconds resolution. > > We can still have the user space interface handing in the information > in nsec resolution, but it's reasonable to scale it down to something > useful. Just shift the incoming information right by 10, so you're in > the 1us resolution for all the internal math and all your limitation > problems are gone. A shift by ten for converting back and forth to > nsecs is not a real performance issue. Just make sure this is well documented in the man pages, and that should eliminate any "surprises". This is a new interface, we can just make this part of the ABI. "The units are in nanoseconds, but all calculations are performed to the nearest microsecond. Take this into account for error analysis". People should be fine with this. -- Steve -- 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/