tools: Use busy waiting in operf

Using nanosleep in between sending SDUs is not accurate enough when
sending thousands of SDUs per second. The --sleep option is added for
lowering CPU consumption in low bandwidth tests.

2 files changed, 24 insertions, 4 deletions

diff --git a/src/tools/operf/operf.c b/src/tools/operf/operf.c
index b52109cf..46dfc14d 100644
--- a/src/tools/operf/operf.c
+++ b/src/tools/operf/operf.c
@@ -41,6 +41,7 @@ struct c {
         int    size;
         long   rate;
         bool   flood;
+        bool   sleep;
         int    duration;
 
         size_t sent;
@@ -81,6 +82,7 @@ static void usage(void)
                "  -r, --rate                Rate (b/s)\n"
                "  -s, --size                Payload size (B, default 1500)\n"
                "  -f, --flood               Send SDUs as fast as possible\n"
+               "      --sleep               Sleep in between sending SDUs\n"
                "      --help                Display this help text and exit\n");
 }
 
@@ -100,6 +102,7 @@ int main(int argc, char ** argv)
         server.timeout = 1000; /* ms */
         client.rate = 1000000;
         client.flood = false;
+        client.sleep = false;
 
         while (argc > 0) {
                 if (strcmp(*argv, "-n") == 0 ||
@@ -127,6 +130,8 @@ int main(int argc, char ** argv)
                 } else if (strcmp(*argv, "-f") == 0 ||
                            strcmp(*argv, "--flood") == 0) {
                         client.flood = true;
+                } else if (strcmp(*argv, "--sleep") == 0) {
+                        client.sleep = true;
                 } else if (strcmp(*argv, "-l") == 0 ||
                            strcmp(*argv, "--listen") == 0) {
                         serv = true;
diff --git a/src/tools/operf/operf_client.c b/src/tools/operf/operf_client.c
index 1f6226d4..902a7b41 100644
--- a/src/tools/operf/operf_client.c
+++ b/src/tools/operf/operf_client.c
@@ -36,6 +36,17 @@
 #include <errno.h>
 #include <float.h>
 
+static void busy_wait_until(const struct timespec * deadline)
+{
+        struct timespec now;
+        clock_gettime(CLOCK_REALTIME, &now);
+        while (now.tv_sec < deadline->tv_sec)
+                clock_gettime(CLOCK_REALTIME, &now);
+        while (now.tv_sec == deadline->tv_sec
+               && now.tv_nsec < deadline->tv_nsec)
+                clock_gettime(CLOCK_REALTIME, &now);
+}
+
 void shutdown_client(int signo, siginfo_t * info, void * c)
 {
         (void) info;
@@ -85,6 +96,7 @@ void * writer(void * o)
         struct timespec now;
         struct timespec start;
         struct timespec intv = {(gap / BILLION), gap % BILLION};
+        struct timespec end = {0, 0};
 
         char * buf = malloc(client.size);
         if (buf == NULL)
@@ -123,6 +135,9 @@ void * writer(void * o)
                 }
         } else {
                 while (ts_diff_ms(&start, &now) < client.duration) {
+                        clock_gettime(CLOCK_REALTIME, &now);
+                        ts_add(&now, &intv, &end);
+
                         if (flow_write(*fdp, buf, client.size) == -1) {
                                 printf("Failed to send SDU.\n");
                                 flow_dealloc(*fdp);
@@ -131,10 +146,10 @@ void * writer(void * o)
                         }
 
                         ++client.sent;
-
-                        nanosleep(&intv, NULL);
-
-                        clock_gettime(CLOCK_REALTIME, &now);
+                        if (client.sleep)
+                                nanosleep(&intv, NULL);
+                        else
+                                busy_wait_until(&end);
                 }
         }