Re: get kernel time && data type

[Erik Mouw <J.A.K.Mouw@ITS.TUDelft.NL>]

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

-- 
J.A.K. (Erik) Mouw, Information and Communication Theory Group, Department
of Electrical Engineering, Faculty of Information Technology and Systems,
Delft University of Technology, PO BOX 5031,  2600 GA Delft, The Netherlands
Phone: +31-15-2783635  Fax: +31-15-2781843  Email: J.A.K.Mouw@its.tudelft.nl
WWW: http://www-ict.its.tudelft.nl/~erik/
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