From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261189AbVGQAob (ORCPT ); Sat, 16 Jul 2005 20:44:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261193AbVGQAob (ORCPT ); Sat, 16 Jul 2005 20:44:31 -0400 Received: from e34.co.us.ibm.com ([32.97.110.132]:23201 "EHLO e34.co.us.ibm.com") by vger.kernel.org with ESMTP id S261189AbVGQAoa (ORCPT ); Sat, 16 Jul 2005 20:44:30 -0400 Date: Sat, 16 Jul 2005 17:44:27 -0700 From: Nishanth Aravamudan To: Pavel Machek Cc: Dave Hansen , Linux Kernel Mailing List Subject: Re: [RFC][PATCH 1/4] add jiffies_to_nsecs() helper and fix up size of usecs Message-ID: <20050717004427.GB5865@us.ibm.com> References: <20050714202629.GD28100@us.ibm.com> <20050714202826.GE28100@us.ibm.com> <1121374488.15263.54.camel@localhost> <20050714210328.GJ28100@us.ibm.com> <20050715121424.GA1775@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050715121424.GA1775@elf.ucw.cz> X-Operating-System: Linux 2.6.13-rc2 (i686) User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 15.07.2005 [14:14:25 +0200], Pavel Machek wrote: > Hi! > > > > > +static inline u64 jiffies_to_nsecs(const unsigned long j) > > > > +{ > > > > +#if HZ <= NSEC_PER_SEC && !(NSEC_PER_SEC % HZ) > > > > + return (NSEC_PER_SEC / HZ) * (u64)j; > > > > +#elif HZ > NSEC_PER_SEC && !(HZ % NSEC_PER_SEC) > > > > + return ((u64)j + (HZ / NSEC_PER_SEC) - 1)/(HZ / NSEC_PER_SEC); > > > > +#else > > > > + return ((u64)j * NSEC_PER_SEC) / HZ; > > > > +#endif > > > > +} > > > > > > That might look a little better something like: > > > > > > static inline u64 jiffies_to_nsecs(const unsigned long __j) > > > { > > > u64 j = __j; > > > > > > if (HZ <= NSEC_PER_SEC && !(NSEC_PER_SEC % HZ)) > > > return (NSEC_PER_SEC / HZ) * j; > > > else if (HZ > NSEC_PER_SEC && !(HZ % NSEC_PER_SEC)) > > > return (j + (HZ / NSEC_PER_SEC) - 1)/(HZ / NSEC_PER_SEC); > > > else > > > return (j * NSEC_PER_SEC) / HZ; > > > } > > > > > > Compilers are smart :) > > > > Well, I was trying to keep it similar to the other conversion functions. > > I guess the compiler can evaluate the conditional full of constants at > > compile-time regardless of whether it is #if or if (). > > > > I can make these changes if others would like them as well. > > Yes, please. And feel free to convert nearby functions, too ;-). I have a patch to make this change for all the jiffies <--> human-time functions, but have a problem. I noticed that these functions, in the if/else form (as opposed to #if/#else) will warn about division-by-zero problems, as (HZ / MSEC_PER_SEC), (HZ / USEC_PER_SEC) & (HZ / NSEC_PER_SEC) are all 0 if HZ < 1000 (which, of course, is the default now :) ). Any suggestions? Just leave the functions as is? Even then, I'm going to update this patch to use USEC_PER_SEC and MSEC_PER_SEC in the other conversion functions like I use NSEC_PER_SEC in the first version. Thanks, Nish