Re: inconsistent do_gettimeofday for copy_page

[Richard B. Johnson]

On Wed, 10 Mar 2004, Ashwin Rao wrote:

> For calculating the time required to copy_page i tried
> the do_gettimeofday for 1000 pages in a loop. But as
> the number of pages changes the time required varies
> non-linearly.
> I also tried reading xtime and using monotonic_clock
> but they didnt help either. For do_gettimeof day for a
> single invocation of copy_page on a pentium 4 gave me
> 10 microsecs but when invoked for a 1000 pages the
> time required was 750ns per page.
> Is there some way of finding out the exact time
> required for copying a page.
>
> Ashwin
>

`rdtsc` on Intel. Gets total CPU clocks. Of course, you will
get jitter unless you disable interrupts during the procedure
you are measuring.


Cheers,
Dick Johnson
Penguin : Linux version 2.4.24 on an i686 machine (797.90 BogoMips).
            Note 96.31% of all statistics are fiction.


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