In the ongoing battle to enlighten the world about the evils of zerofilling memory pages, you can make your contribution right now! If you have a machine at your disposal, that is not a G4-400 Mhz G3-350 Mhz, iBook 500 Mhz or iMac 800 Mhz you immediately qualify.
How's that ? Pretty easy requirements! Please compile and run the following code on a system that is close to doing nothing, turn of Mail, turn off iTunes and what ever else might be sucking up CPU time. Compile this with cc -o page-clean-test page-clean-test.m -framework Foundation.
Please send the output result to nat@mulle-kybernetik.com (Harvest be damn SPAM bot!) Please write me the kind of system you ran the test on. If you didn't use Mac OS X 10.2, please tell me also.
Here comes the source...
#import <Foundation/Foundation.h>
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <unistd.h>
#include <mach/mach_init.h>
#include <mach/vm_map.h>
#include <mach/vm_statistics.h>
/* Try this to see cost of zero page faulting
* in relationship to allocate and deallocate
* PAGES=1 LOOPS=200000
*/
#define PAGES 1
#define LOOPS (1000*1000)
/* Try this to see cost of zero page faulting
* in relationship to "other activtity" during
* faulting. Some believe zerofill is cheap.
* Check it out with Shark. Use a little fuzz,
* set samples to 50 us and let run for 300000
* samples or so
* PAGES=2048 LOOPS=1000
*/
void alloc_loop()
{
unsigned int i;
char *block;
for( i = 0; i < LOOPS; i++)
{
if( vm_allocate( mach_task_self(), (vm_address_t *) &block, PAGES * vm_page_size, 1))
abort();
if( vm_deallocate( mach_task_self(), (vm_address_t) block, PAGES * vm_page_size))
abort();
}
}
void touch_loop()
{
unsigned int i, j;
char *block;
for( i = 0; i < LOOPS; i++)
{
if( vm_allocate( mach_task_self(), (vm_address_t *) &block, PAGES * vm_page_size, 1))
abort();
for( j = 0; j < PAGES * vm_page_size; j += vm_page_size)
block[ j] = 1;
if( vm_deallocate( mach_task_self(), (vm_address_t) block, PAGES * vm_page_size))
abort();
}
}
void alloc_loop2()
{
unsigned int i;
char *block;
for( i = 0; i < LOOPS; i++)
{
if( vm_allocate( mach_task_self(), (vm_address_t *) &block, PAGES * 2 * vm_page_size, 1))
abort();
if( vm_deallocate( mach_task_self(), (vm_address_t) block, PAGES * 2 * vm_page_size))
abort();
}
}
void touch_loop2()
{
unsigned int i, j;
char *block;
for( i = 0; i < LOOPS; i++)
{
if( vm_allocate( mach_task_self(), (vm_address_t *) &block, PAGES * 2 * vm_page_size, 1))
abort();
for( j = 0; j < PAGES * 2 * vm_page_size; j += vm_page_size)
block[ j] = 1;
if( vm_deallocate( mach_task_self(), (vm_address_t) block, PAGES * 2 * vm_page_size))
abort();
}
}
int main()
{
alloc_loop(); /* warm up */
NSLog( @"Just alloc start\n");
alloc_loop();
NSLog( @"Just alloc stop\n");
NSLog( @"Zero fill start\n");
touch_loop();
NSLog( @"Zero fill stop\n");
NSLog( @"Just alloc start two pages\n");
alloc_loop2();
NSLog( @"Just alloc stop two pages\n");
NSLog( @"Zero fill start two pages\n");
touch_loop2();
NSLog( @"Zero fill stop two pages\n");
return( 0);
}