Re: HZ, preferably as small as possible

Russell King (rmk@arm.linux.org.uk)
Mon, 15 Jul 2002 18:06:46 +0100

On Mon, Jul 15, 2002 at 12:07:18PM -0400, Albert D. Cahalan wrote:
> You have 64, 128, and 1000. See for yourself.
>
> arch-cl7500/param.h #define HZ 100
> arch-epxa10db/param.h #define HZ 100
> arch-integrator/param.h #define HZ 100
> arch-l7200/param.h #define HZ 128
> arch-shark/param.h #define HZ 64
> arch-tbox/param.h #define HZ 1000
>
> I need to support all of that with one binary.
> So I'm stuck with:

Lets look more closely:

#ifndef HZ
#define HZ 100
#endif
#if defined(__KERNEL__) && (HZ == 100)
#define hz_to_std(a) (a)
#endif

And:

$ grep hz_to_std arch-*/param.h
arch-l7200/param.h:#define hz_to_std(a) ((a * HZ)/100)
arch-shark/param.h:#define hz_to_std(a) ((a * HZ)/100)

As I said, tbox is broken, so ignore that.

And hz_to_std gets used (fs/proc/array.c):

hz_to_std(task->times.tms_utime),
hz_to_std(task->times.tms_stime),
hz_to_std(task->times.tms_cutime),
hz_to_std(task->times.tms_cstime),

So merely grepping for HZ doesn't actually tell you anything.

All /proc values are in 100Hz units on ARM.

-- 
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html


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