From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: MSEC_TO_JIFFIES is messed up... Date: Wed, 12 May 2004 22:28:07 +0200 Sender: netdev-bounce@oss.sgi.com Message-ID: <20040512202807.GA16849@elte.hu> References: <20040512020700.6f6aa61f.akpm@osdl.org> <20040512181903.GG13421@kroah.com> <40A26FFA.4030701@pobox.com> <20040512193349.GA14936@elte.hu> <200405121947.i4CJlJm5029666@turing-police.cc.vt.edu> <200405122007.i4CK7GPQ020444@turing-police.cc.vt.edu> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="bg08WKrSYDhXBjb5" Cc: Davide Libenzi , Jeff Garzik , Greg KH , Andrew Morton , linux-kernel@vger.kernel.org, Netdev Return-path: To: Valdis.Kletnieks@vt.edu Content-Disposition: inline In-Reply-To: <200405122007.i4CK7GPQ020444@turing-police.cc.vt.edu> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org --bg08WKrSYDhXBjb5 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline * Valdis.Kletnieks@vt.edu wrote: > The problem is that even for the i386 family, there's no inherent > reason why the value of HZ is nailed to 1000 [...] The code is 100% correct, but not 100% clean, and definitely not documented. The reason for the change was to avoid unnecessary integer multiplications and divisions in sched.c. the attached patch (against BK-curr) cleans this up and makes the defines generic and arch-independent. Ingo --bg08WKrSYDhXBjb5 Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="hz-cleanup-2.6.6-A0" --- linux/include/linux/time.h.orig +++ linux/include/linux/time.h @@ -177,6 +177,15 @@ struct timezone { (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1) #endif + +#if HZ == 1000 +# define JIFFIES_TO_MSEC(x) (x) +# define MSEC_TO_JIFFIES(x) (x) +#else +# define JIFFIES_TO_MSEC(x) ((x) * 1000 / HZ) +# define MSEC_TO_JIFFIES(x) ((x) * HZ / 1000) +#endif + /* * The TICK_NSEC - 1 rounds up the value to the next resolution. Note * that a remainder subtract here would not do the right thing as the --- linux/include/asm-i386/param.h.orig +++ linux/include/asm-i386/param.h @@ -5,8 +5,6 @@ # define HZ 1000 /* Internal kernel timer frequency */ # define USER_HZ 100 /* .. some user interfaces are in "ticks" */ # define CLOCKS_PER_SEC (USER_HZ) /* like times() */ -# define JIFFIES_TO_MSEC(x) (x) -# define MSEC_TO_JIFFIES(x) (x) #endif #ifndef HZ --- linux/kernel/sched.c.orig +++ linux/kernel/sched.c @@ -75,13 +75,6 @@ #define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ)) #define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ)) -#ifndef JIFFIES_TO_MSEC -# define JIFFIES_TO_MSEC(x) ((x) * 1000 / HZ) -#endif -#ifndef MSEC_TO_JIFFIES -# define MSEC_TO_JIFFIES(x) ((x) * HZ / 1000) -#endif - /* * These are the 'tuning knobs' of the scheduler: * --bg08WKrSYDhXBjb5--