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


From: andrzej zaborowski
Subject: Re: [Qemu-devel] Patch: cpu-all.h for better cycle counter
Date: Mon, 26 Mar 2007 00:07:16 +0200

Hi,

On 21/03/07, Todd T. Fries <address@hidden> 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 .. address@hidden

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Regards,
Andrew




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