audiod: Don't compute stat info unnecessarily.

Currently we compute this information in each scheduler iteration
and check whether it has changed since the last time we sent it to
the stat clients.

This is quite expensive, so this patch teaches para_audiod to only look
at the status items if the last write time was more than 500ms ago.

diff --git a/audiod.c b/audiod.c
index 9ed319f4c27ab7e202082552f1a0ffa9328fe60f..5ef5778107e22dd44e44402f2961cc0f6192a594 100644 (file)
--- a/audiod.c
+++ b/audiod.c
@@ -1031,22 +1031,35 @@ static int command_post_select(struct sched *s, struct task *t)
        int ret;
        struct command_task *ct = container_of(t, struct command_task, task);
        static struct timeval last_status_dump;
-       struct timeval tmp, delay = {5, 0};
-       bool force = false;
-
-       tv_add(&last_status_dump, &delay, &tmp);
-       if (tv_diff(&tmp, now, NULL) < 0) {
-               last_status_dump = *now;
-               force = true;
-       }
+       struct timeval tmp, delay;
+       bool force = true;
 
        ret = handle_connect(ct->fd, &s->rfds);
        if (ret < 0)
                PARA_ERROR_LOG("%s\n", para_strerror(-ret));
        else if (ret > 0)
-               force = true;
+               goto dump;
+
+       /* if last status dump was less than 500ms ago, do nothing */
+       delay.tv_sec = 0;
+       delay.tv_usec = 500 * 1000;
+       tv_add(&last_status_dump, &delay, &tmp);
+       if (tv_diff(now, &tmp, NULL) < 0)
+               return 0;
+
+       /*
+        * If last status dump was more than 5s ago, force update. Otherwise,
+        * update only those items that have changed.
+        */
+       delay.tv_sec = 5;
+       delay.tv_usec = 0;
+       tv_add(&last_status_dump, &delay, &tmp);
+       if (tv_diff(now, &tmp, NULL) < 0)
+               force = false;
+dump:
        audiod_status_dump(force);
-       return 0;
+       last_status_dump = *now;
+       return 1;
 }
 
 static void init_command_task(struct command_task *ct)