Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751464AbZGaHqI (ORCPT ); Fri, 31 Jul 2009 03:46:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751372AbZGaHqH (ORCPT ); Fri, 31 Jul 2009 03:46:07 -0400 Received: from mtagate8.de.ibm.com ([195.212.29.157]:49886 "EHLO mtagate8.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751355AbZGaHqG (ORCPT ); Fri, 31 Jul 2009 03:46:06 -0400 Date: Fri, 31 Jul 2009 09:45:49 +0200 From: Martin Schwidefsky To: john stultz Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner , Daniel Walker Subject: Re: [RFC][patch 11/12] timekeeper read clock helper functions Message-ID: <20090731094549.335fb996@skybase> In-Reply-To: <1248989994.3374.13.camel@localhost> References: <20090729134125.313191633@de.ibm.com> <20090729134231.768960500@de.ibm.com> <1248989994.3374.13.camel@localhost> 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 Content-Length: 2644 Lines: 70 On Thu, 30 Jul 2009 14:39:54 -0700 john stultz wrote: > On Wed, 2009-07-29 at 15:41 +0200, Martin Schwidefsky wrote: > > plain text document attachment (timekeeper-helper.diff) > > From: Martin Schwidefsky > > > > Add timekeeper_read_clock_ntp and timekeeper_read_clock_raw and use > > them for getnstimeofday, ktime_get, ktime_get_ts and getrawmonotonic. > > > > Cc: Ingo Molnar > > Cc: Thomas Gleixner > > Cc: john stultz > > Cc: Daniel Walker > > Signed-off-by: Martin Schwidefsky > > --- > > kernel/time/timekeeping.c | 91 +++++++++++++++++++--------------------------- > > 1 file changed, 38 insertions(+), 53 deletions(-) > > > > Index: linux-2.6/kernel/time/timekeeping.c > > =================================================================== > > --- linux-2.6.orig/kernel/time/timekeeping.c > > +++ linux-2.6/kernel/time/timekeeping.c > > @@ -84,6 +84,40 @@ static void timekeeper_setup_internals(s > > timekeeper.shift = clock->shift; > > } > > > > +/* Timekeeper helper functions. */ > > +static inline s64 timekeeper_read_clock_ntp(void) > > +{ > > + cycle_t cycle_now, cycle_delta; > > + struct clocksource *clock; > > + > > + /* read clocksource: */ > > + clock = timekeeper.clock; > > + cycle_now = clock->read(clock); > > + > > I know it seems nice to have it here, but I think these helpers would be > more reusable in other contexts if they took the cycle_now value as an > argument. Also I'd drop the ntp bit, just to avoid confusing it with > some ntp specific function. So: > > timekeeping_get_ns(cycle_t now); > timekeeping_get_ns_raw(cycle_t now); > > That way in some situations we don't have to make two accesses to the > hardware if we want to get both values at the same point. > > Seem reasonable? The new names are fine but if we pull out the ->read call to the caller we again have a rather strange mix. The caller gets the cycle value using some clock, the helper uses the value of the timekeeper clock or the timerkeeper mult/shift. I would like to keep the ->read call in the helper. Is there a situation where we need both calculations for the same cycles value? There is none in the current code as far as I can see. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- 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/