关于本章
wikipedia Processor affinity
sched_setaffinity
man 2 sched_setaffinity
Example1
来源：
原文中的程序是无法编译通过的，下面是对其更正后，可以编译通过的版本：
/* Short test program to test sched_setaffinity
* (which sets the affinity of processes to processors).
* Compile: gcc sched_setaffinity_test.c
* -o sched_setaffinity_test -lm
* Usage: ./sched_setaffinity_test
*
* Open a "top"-window at the same time and see all the work
* being done on CPU 0 first and after a short wait on CPU 1.
* Repeat with different numbers to make sure, it is not a
* coincidence.
*/
#include <stdio.h>
#include <math.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
double waste_time(long n)
{
double res = 0;
long i = 0;
while (i < n * 200000)
{
i++;
res += sqrt(i);
}
return res;
}
int main(int argc, char **argv)
{
unsigned long mask = 1; /* processor 0 */
cpu_set_t set;
CPU_SET(mask, &set);
/* bind process to processor 0 */
if (sched_setaffinity(getpid(), sizeof(set), &set) < 0)
{
perror("sched_setaffinity");
}
/* waste some time so the work is visible with "top" */
printf("result: %f\n", waste_time(2000));
mask = 2; /* process switches to processor 1 now */
CPU_SET(mask, &set);
if (sched_setaffinity(getpid(), sizeof(set), &set) < 0)
{
perror("sched_setaffinity");
}
/* waste some more time to see the processor switch */
printf("result: %f\n", waste_time(2000));
}
编译指令：gcc test.cpp -lm
Example 2
来源：sched_setaffinity(2) — Linux manual 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);
}
}