Re: get kernel time && data type

["alejandro alliana" <aalliana@hotmail.com>]

tks very  much.

  It seems to me jiffies isn't as accurate as i need.
  I followed your advice and tried:
   long t1;
   rdtscl(ts);
  but 4 bytes isn't enogh time (i get the same number aprox every  12 sec.), 
I'd much rather use 8 bytes using an unsigned long long )

   __asm__ volatile(".byte 0x0f,0x31" : "=A" (x));
but have been having trouble with the compilation when using an unsigned 
long long int variable in the kernel source.  The error message is:

mm/mm.o: In function `refresh_input':
mm/mm.o(.text+0xa0be): undefined reference to `__cmpdi2'
mm/mm.o: In function `NN_train':
mm/mm.o(.text+0xab0c): undefined reference to `__cmpdi2'
make: *** [vmlinux] Error 1

Alejandro


>On Wed, Mar 14, 2001 at 06:55:05AM -0600, alejandro alliana wrote:
> >   I need to keep track of the time when a page is
> > swapped in (out), with a presicion of about
> > milliseconds or microseconds. I would like to know a
> > way to get the time when that happens and what data
> > type would be good for this and be reasonable easy to
> > do some arithmetic operations with it.
> >
> >   I've been using so far jiffies (unsigned long) but
> > it seems the time presicion is not very good because i
> > always get the same time.
>
>Then you're doing something wrong because jiffies *is* updated every
>1/HZ second and quite a lot of drivers will break if it doesn't.
>
> >  I also tried to read the
> > time stamp counter (to an unsigned long long )with the
> > line
> >   __asm__ volatile(".byte 0x0f,0x31" : "=A" (x));
> > but have been having trouble with the compilation.
>
>   #include <asm/msr.h>
>
>   long t1;
>   rdtscl(ts);
>
> >   What other options do I have or am I on the right
> > track?
>
>Sounds to me like you're doing something wrong. I know that Adam
>Wiggins used exactly the same trick with jiffies to keep track of pages
>and TLB entries (for fast address space switching on StrongARM CPUs).
>
>
>Erik

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