From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760128AbZBDVPc (ORCPT ); Wed, 4 Feb 2009 16:15:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756134AbZBDVPR (ORCPT ); Wed, 4 Feb 2009 16:15:17 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.144]:57104 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756129AbZBDVPP (ORCPT ); Wed, 4 Feb 2009 16:15:15 -0500 Subject: Re: [PATCH NET-NEXT 01/10] clocksource: allow usage independent of timekeeping.c From: john stultz To: Daniel Walker Cc: Patrick Ohly , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , David Miller , Thomas Gleixner In-Reply-To: <1233781499.15119.135.camel@desktop> References: <1233752517-30010-1-git-send-email-patrick.ohly@intel.com> <1233752517-30010-2-git-send-email-patrick.ohly@intel.com> <1233756235.15119.54.camel@desktop> <1233758796.15940.198.camel@ecld0pohly> <1233760170.15119.76.camel@desktop> <1233775542.6994.13.camel@localhost.localdomain> <1233776421.15119.125.camel@desktop> <1233777982.6994.51.camel@localhost.localdomain> <1233781499.15119.135.camel@desktop> Content-Type: text/plain Date: Wed, 04 Feb 2009 13:15:00 -0800 Message-Id: <1233782100.6994.82.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2009-02-04 at 13:04 -0800, Daniel Walker wrote: > On Wed, 2009-02-04 at 12:06 -0800, john stultz wrote: > > > The duplication is only at a very low level. He could not reuse the > > established clocksource system without really breaking its semantics. > > He gave a link to the first version, > > http://kerneltrap.org/mailarchive/linux-netdev/2008/11/19/4164204 > > What specific semantics is he breaking there? His re-usage of cycle_last and xtime_nsec for other means then how they're defined. In that case his use of xtime_nsec doesn't even store the same unit. Plus he adds other accessors to the clocksource structure that are not compatible with the clocksources registered for timekeeping. He's really doing something different here, and while it does access a counter, and it does translate that into nanoseconds, its not the same as whats done in the timekeeping core which the clocksource was designed around. So by creating his own infrastructure in a shared manner, splitting out a chunk of it to be reused in the clocksource/timekeeping core I think is really a good thing and the right approach. thanks -john