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Re: [Qemu-devel] Patch: cpu-all.h for better cycle counter
From: |
Marc Lörner |
Subject: |
Re: [Qemu-devel] Patch: cpu-all.h for better cycle counter |
Date: |
Mon, 26 Mar 2007 13:52:54 +0100 |
User-agent: |
KMail/1.6.2 |
On Monday 26 March 2007 00:08, andrzej zaborowski wrote:
> On 26/03/07, andrzej zaborowski <address@hidden> wrote:
<snip>
> > > +# 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)
I dont think so, in the loop "j" is set and the while-condition is "j==i",
so unless "(tv.tv_sec * (uint64_t) 1000000) + tv.tv_usec" always computes the
same value the do-while block gets only executed once.
>
<snip>
--
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