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

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

On 26/03/07, andrzej zaborowski <balrog@zabor.org> wrote:
> 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.

(I wanted to say MHz)

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