Added affinity example in chapter 6

chp6/affinity.c

@@ -0,0 +1,25 @@
+#define _GNU_SOURCE
+#include <sched.h>
+#include <stdio.h>
+
+int main(void)
+{
+	cpu_set_t set;
+	CPU_ZERO(&set);
+	CPU_SET(0, &set);
+	CPU_CLR(1, &set);
+
+	int ret = sched_setaffinity(0, sizeof(cpu_set_t), &set);
+	if (ret == -1) {
+		perror("sched_setaffinity");
+	}
+
+	for (int i = 0; i < CPU_SETSIZE; i++) {
+		int cpu = CPU_ISSET(i, &set);
+		if (cpu) {
+			printf("cpu=%d is set\n", i);
+		}
+	}
+
+	return 0;
+}