FPS Calculation Program

[Monk]

/*-
* Copyright (c) 2006, 2007, 2008 Gary Stanley (gary@summit-servers.com)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#include    <stdio.h>
#include	"stdafx.h"
#include	"windows.h"
#pragma comment ( lib, "winmm.lib" ) 
       
int 
main(void)
{

/*
One of the major problems with FPS calculation is cache line bouncing/cache stalls due to prefetching
There is no magic bullet to make things work. They either work, or they don't. 
*/

const int count = 512;
   	printf("This program estimates gameserver FPS and displays the results.\n");
printf("The results of this program are rounded to the nearest int / 1000\n");
printf("\n");

timeBeginPeriod(1); /* Needed for low latency Sleeps */
   	int its = 0;
   	long cur = 0, last = timeGetTime();
   	while (its < count) {
 cur = timeGetTime();
   if (cur != last) {
     last = cur;
            its++;
        }
   	}
printf("Testing Sleep(1) granularity :\n");
   	long first = timeGetTime();
   	cur = first;
   	last = first;
   	for (int n=0; n<count; n++) {
       Sleep(1); 
       cur = timeGetTime();
printf("Wakeup Latency: %dms Estimated Maximum FPS: %d\n", cur-last, (1000 / (cur-last) ) );
last = cur;
   }
getchar(); 
}

 

This more or less shows how long a sleep(1) really sleeps. It is currently rounded to the nearest hundreth of a MS, and it rounds down or up depending on a number of things.

 

Anyways, I used this for quite a few years to debug hardware to see why FPS/tickrate wouldn't remain the same even though there was nothing running.

 

This has other uses, too, if you want to figure out if a machine has too many servers fighting for a scheduler quantum...

 

I'm currently working on something that shows how long a sleep(1) really takes, down to the microsecond with rdtsc and some other non-windows tricks.

FPS estimator.zip

[Derek]

Thanks Monk=/

[Monk]

oops.

 

try this one instead..

FPS estimator.zip

[Monk]

On windows 2003 sometimes the sleep latency will drop down to about 1.95, so its rounding the value down. until i rewrite the functions its more or less generally estimated ..

[Steven Crothers]

Nice, very accurate.