Re: MSEC_TO_JIFFIES is messed up...
From: Ingo Molnar
Date: Wed May 12 2004 - 15:12:08 EST
* Davide Libenzi <davidel@xxxxxxxxxxxxxxx> wrote:
> > why is it wrong?
> For HZ == 1000 it's fine, even if it'd better to explicitly make it HZ
> dependent and let the compiler to discard them.
the compiler cannot discard the multiplication and the division from the
x * 1000 / 1000
due to overflows. But we know that HZ is 1000 in the arch-dependent
param.h, and in sched.c we use the HZ dependent variant:
# define JIFFIES_TO_MSEC(x) ((x) * 1000 / HZ)
# define MSEC_TO_JIFFIES(x) ((x) * HZ / 1000)
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