Messages in this thread Patch in this message | | | Date | Wed, 12 May 2004 22:28:07 +0200 | From | Ingo Molnar <> | Subject | Re: MSEC_TO_JIFFIES is messed up... |
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* Valdis.Kletnieks@vt.edu <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 --- 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: *
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