From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754896AbZHNLM5 (ORCPT ); Fri, 14 Aug 2009 07:12:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754731AbZHNLM4 (ORCPT ); Fri, 14 Aug 2009 07:12:56 -0400 Received: from mtagate1.de.ibm.com ([195.212.17.161]:52749 "EHLO mtagate1.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754533AbZHNLM4 (ORCPT ); Fri, 14 Aug 2009 07:12:56 -0400 Date: Fri, 14 Aug 2009 13:12:54 +0200 From: Martin Schwidefsky To: john stultz Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner , Daniel Walker Subject: Re: [patch 11/14] timekeeper read clock helper functions Message-ID: <20090814131254.0ef001a2@skybase> In-Reply-To: <1250206218.7149.13.camel@localhost.localdomain> References: <20090813154034.613706651@de.ibm.com> <20090813154201.810817188@de.ibm.com> <1250206218.7149.13.camel@localhost.localdomain> Organization: IBM Corporation X-Mailer: Claws Mail 3.7.2 (GTK+ 2.16.5; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 13 Aug 2009 16:30:18 -0700 john stultz wrote: > On Thu, 2009-08-13 at 17:40 +0200, Martin Schwidefsky wrote: > > Index: linux-2.6/kernel/time/timekeeping.c > > =================================================================== > > --- linux-2.6.orig/kernel/time/timekeeping.c > > +++ linux-2.6/kernel/time/timekeeping.c > > @@ -95,6 +95,40 @@ static void timekeeper_setup_internals(s > > timekeeper.mult = clock->mult; > > } > > > > +/* Timekeeper helper functions. */ > > +static inline s64 timekeeping_get_ns(void) > > +{ > > + cycle_t cycle_now, cycle_delta; > > + struct clocksource *clock; > > + > > + /* read clocksource: */ > > + clock = timekeeper.clock; > > + cycle_now = clock->read(clock); > > + > > + /* calculate the delta since the last update_wall_time: */ > > + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; > > + > > + /* return delta convert to nanoseconds using ntp adjusted mult. */ > > + return clocksource_cyc2ns(cycle_delta, timekeeper.mult, > > + timekeeper.shift); > > +} > > Again, not a huge issue, but if we kept the read() out of this function > and instead passed the cycle_now value in as a argument, we could also > use this function in timekeeping_forward_now() I actually tested how the code would look like if I do that. Didn't like the result. The thing is that timekeeping_get_ns is a helper that is supposed to reduce the number of lines you need in the caller. If you push clock->read(clock) call back into the caller it doesn't help much .. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.