On 9/26/06, Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote:
Hi folks...
recently I did a simple experiment, that was running a CPU bound program
on Linux kernels with different HZ setting. I pick three, HZ=100,
HZ=250 and HZ=250. Here is the result:
HZ=100 HZ=250 HZ=1000
Real 319.326 317.786 319.072
User 319.33 317.801 319.094
System 0 0.001 0
The result was taken by simply running the program with "time" command.
The programs were ran 4 time each and the average was calculate for all
real, user and system time.
If you look closely, perhaps you will be shocked with the number. On
HZ=250, the program seems running faster than the other two. I almost
can believe it, as I suspected that it should run slower due to more
work on taking care the interrupts. Anybody can kindly explain what
happened here?
Here is the program I used for the test:
#include<stdio.h>
#include<stdlib.h>
int main(int argc, char *argv[])
{
int i, j;
long int l, m;
unsigned long int k,loop_max;
float hasil;
if (argc >= 2) {
loop_max = labs(strtoul(argv[1], (char **) NULL, 10));
} else
loop_max = 1000;
printf("loop_max is %lu\n", loop_max);
for (i = 0; i <= 3000; i++)
for (j = 0; j <= 1000; j++)
for (k = 0; k <= loop_max; k++) {
l = random();
do {
m = random();
Hi Mulyadi,
One thing I doubt here is the random function. As you are using
random, it might be making the total runtime of this program different
for every run, hope you get what I mean to say ....
moreover I think you will see the improvement in cpu times as HZ
increases to some limit and then it falls down. As you increase the
HZ, you make system to respond more quickly to events, but increasing
this HZ value to large value will degrate the stats just because you
are spending more time in handling interrup than doing something
usefull. So the curve for system response with increase in HZ goes in
bell shape, this is what i think .... not sure about it.
regards,
Gaurav
} while (m == 0);
hasil = l / m;
}
return (0);
}
regards,
Mulyadi
--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive: http://mail.nl.linux.org/kernelnewbies/
FAQ: http://kernelnewbies.org/faq/
--
Gaurav
Email: gauravd.chd@xxxxxxxxx
--------------------------------------------
Read my articles at: http://lkdp.blogspot.com
--------------------------------------------
Easy to get air tickets at affordable price,
US to India Air Tickets: www.Ritz-Travel.com
Call at 001-503-848-2299 or mail at info@xxxxxxxxxxxxxxx
--------------------------------------------
--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive: http://mail.nl.linux.org/kernelnewbies/
FAQ: http://kernelnewbies.org/faq/
