Re: [Qemu-devel] Patch: cpu-all.h for better cycle counter

["andrzej zaborowski" <balrog@zabor.org>]

Hi,

On 21/03/07, Todd T. Fries <todd@fries.net> wrote:
> This is relative to the 20070319 snapshot.
>
> --- cpu-all.h.orig      Fri Mar 16 18:58:11 2007
> +++ cpu-all.h   Tue Mar 20 21:14:10 2007
> @@ -1012,13 +1012,22 @@ static inline int64_t cpu_get_real_ticks
>  #endif
>  }
>  #else
> -/* The host CPU doesn't have an easily accessible cycle counter.
> -   Just return a monotonically increasing vlue.  This will be totally wrong,
> -   but hopefully better than nothing.  */
> +# warning non-optimized CPU
> +#include <sys/time.h>
> +#include <time.h>
> +
>  static inline int64_t cpu_get_real_ticks (void)
>  {
> -    static int64_t ticks = 0;
> -    return ticks++;
> +       struct timeval tv;
> +       static int64_t i = 0;
> +       int64_t j;
> +
> +       gettimeofday(&tv, NULL);
> +       do {
> +          j = (tv.tv_sec * (uint64_t) 1000000) + tv.tv_usec;
> +       } while (i == j);
> +       i = j;
> +       return j;

Isn't this an infinite loop? gettimeofday() was left out of the loop.

How about "return j + (ticks++)" instead of the loop? If I understand
correctly it may slow things down to below 1Hz.

>  }
>  #endif
>
> --
> Todd Fries .. todd@fries.net
>
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Regards,
Andrew