running gzip on sigle core in muticore environment under unix - gzip

Question

I have a requirement to use only single core to test gzip performance in multi-core cpu environment(not sure what is the default settings for gzip in this case). Need help to find out the command to execute gzip compression in single core.
Thanks

Answer 1

gzip is single threaded by default so in effect it will look like it's running on one core ie it might run on several physical cores but it won't be in parallel.
If you absolutely must run on one core and you're on linux you would set affinity to a particular core.
http://man7.org/linux/man-pages/man2/sched_setaffinity.2.html
This is code that I got from the man page.
#define _GNU_SOURCE
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \
} while (0)
int
main(int argc, char *argv[])
{
cpu_set_t set;
int parentCPU, childCPU;
int nloops, j;
if (argc != 4) {
fprintf(stderr, "Usage: %s parent-cpu child-cpu num-loops\n",
argv[0]);
exit(EXIT_FAILURE);
}
parentCPU = atoi(argv[1]);
childCPU = atoi(argv[2]);
nloops = atoi(argv[3]);
CPU_ZERO(&set);
switch (fork()) {
case -1: /* Error */
errExit("fork");
case 0: /* Child */
CPU_SET(childCPU, &set);
if (sched_setaffinity(getpid(), sizeof(set), &set) == -1)
errExit("sched_setaffinity");
for (j = 0; j < nloops; j++)
getppid();
exit(EXIT_SUCCESS);
default: /* Parent */
CPU_SET(parentCPU, &set);
if (sched_setaffinity(getpid(), sizeof(set), &set) == -1)
errExit("sched_setaffinity");
for (j = 0; j < nloops; j++)
getppid();
wait(NULL); /* Wait for child to terminate */
exit(EXIT_SUCCESS);
}
}
If you need to test with no interruptions from the kernel you need to write a kernel module for that.