Add CPU affinity option to server and client

packet-exchange/src/client.c

+#define _GNU_SOURCE
+
 #include <errno.h>
 #include <error.h>
 #include <pthread.h>
@@ -22,6 +24,9 @@ typedef struct thread_param {
   int interval;
   int priority;
   int max_cycles;
+
+  int enable_affinity;
+
   const char *ip_address;
   thread_stat_t stats;
 } thread_param_t;
@@ -39,13 +44,24 @@ static void *packet_sending_thread(void *p) {
   struct timespec next;
   struct sched_param priority;
   thread_param_t *param = (thread_param_t *)p;
+  cpu_set_t mask;
+
+  if(param->enable_affinity) {
+    // Set thread CPU affinity
+    CPU_ZERO(&mask);
+    CPU_SET(1, &mask);
+    if (sched_setaffinity(0, sizeof(mask), &mask))
+      fprintf(stderr, "Could not set CPU affinity to CPU #1\n");
+  }
 
+  // Set thread priority
   priority.sched_priority = param->priority;
   if (sched_setscheduler(0, SCHED_FIFO, &priority))
     error(EXIT_FAILURE, errno, "Couldn't set priority");
 
   clock_gettime(CLOCK_ID, &next);
 
+  // Packet sending loop
   for (param->stats.nb_cycles = 0;; param->stats.nb_cycles++) {
     if (param->max_cycles)
       if (param->stats.nb_cycles >= param->max_cycles) break;
@@ -104,11 +120,14 @@ int main(int argc, char *argv[]) {
 static void process_options(int argc, char *argv[], thread_param_t *param,
                             main_param_t *main_param) {
   for (;;) {
-    int c = getopt(argc, argv, "i:l:p:r:");
+    int c = getopt(argc, argv, "ai:l:p:r:");
 
     if (c == -1) break;
 
     switch (c) {
+      case 'a':
+        param->enable_affinity = 1;
+        break;
       case 'i':
         param->interval = atoi(optarg) * 1000;
         break;

packet-exchange/src/server.c

+#define _GNU_SOURCE
+
 #include <arpa/inet.h>
 #include <errno.h>
 #include <error.h>
@@ -30,6 +32,8 @@ typedef struct thread_param {
   int priority;
   thread_stat_t stats;
 
+  int enable_affinity;
+
   int sockfd;
 } thread_param_t;
 
@@ -53,6 +57,7 @@ static void *packet_receiving_thread(void *p) {
   thread_param_t *param = (thread_param_t *)p;
   thread_stat_t *stats = &param->stats;
   uint64_t diff = 0;
+  cpu_set_t mask;
 
   char buf[BUFFER_SIZE];
   int bytes_received = 0;
@@ -64,10 +69,20 @@ static void *packet_receiving_thread(void *p) {
   stats->min_interval = UINT64_MAX;
   stats->max_interval = 0;
 
+  if(param->enable_affinity) {
+    // Set thread CPU affinity
+    CPU_ZERO(&mask);
+    CPU_SET(1, &mask);
+    if (sched_setaffinity(0, sizeof(mask), &mask))
+      fprintf(stderr, "Could not set CPU affinity to CPU #1\n");
+  }
+
+  // Set thread priority
   priority.sched_priority = param->priority;
   if (sched_setscheduler(0, SCHED_FIFO, &priority))
     error(EXIT_FAILURE, errno, "Couldn't set priority");
 
+  // Packet receiving loop
   for (stats->packets_received = 0;; stats->packets_received++) {
     bytes_received = recvfrom(param->sockfd, buf, BUFFER_SIZE - 1, 0,
                               (struct sockaddr *)&client_addr, &addr_len);
@@ -124,11 +139,14 @@ int main(int argc, char *argv[]) {
 static void process_options(int argc, char *argv[], thread_param_t *param,
                             main_param_t *main_param) {
   for (;;) {
-    int c = getopt(argc, argv, "p:r:");
+    int c = getopt(argc, argv, "ap:r:");
 
     if (c == -1) break;
 
     switch (c) {
+      case 'a':
+        param->enable_affinity = 1;
+        break;
       case 'p':
         param->priority = atoi(optarg);
         break;