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Full Discussion: RDTSC use in C:
Top Forums Programming RDTSC use in C: Post 302324893 by otheus on Friday 12th of June 2009 06:47:03 AM
Old 06-12-2009
Sivaraman,

I need to re-phrase your question --- please tell me if this is correct: How does one find out (on Linux) whether the CPU is actually running at the speed specified in cpuinfo?

Instead of the sleep statement above, set an alarm for 10 seconds, do some CPU-intensive work, get the number of ticks, compare the clocks to find how long the CPU actually slept (setting an alarm does not guarantee anything) and calculate. Use gettimeofday() to get the actual time.
 
SLEEP(3)								 1								  SLEEP(3)

sleep - Delay execution

SYNOPSIS
int sleep (int $seconds) DESCRIPTION
Delays the program execution for the given number of $seconds. PARAMETERS
o $seconds - Halt time in seconds. RETURN VALUES
Returns zero on success, or FALSE on error. If the call was interrupted by a signal, sleep(3) returns a non-zero value. On Windows, this value will always be 192 (the value of the WAIT_IO_COMPLETION constant within the Windows API). On other platforms, the return value will be the number of seconds left to sleep. ERRORS
/EXCEPTIONS If the specified number of $seconds is negative, this function will generate a E_WARNING. CHANGELOG
+--------+---------------------------------------------------+ |Version | | | | | | | Description | | | | +--------+---------------------------------------------------+ | 5.3.4 | | | | | | | Before PHP 5.3.4, on Windows, sleep(3) always | | | returns NULL when sleep has occurred, regardless | | | of whether the sleep was interrupted or not. | | | | +--------+---------------------------------------------------+ EXAMPLES
Example #1 sleep(3) example <?php // current time echo date('h:i:s') . " "; // sleep for 10 seconds sleep(10); // wake up ! echo date('h:i:s') . " "; ?> This example will output (after 10 seconds) 05:31:23 05:31:33 SEE ALSO
usleep(3), time_nanosleep(3), time_sleep_until(3), set_time_limit(3). PHP Documentation Group SLEEP(3)
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