lib: flush ready queue before poll() again

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>

diff --git a/lib/thread.c b/lib/thread.c
index 5db470ef488b843472da3d829e243378aed7fe1c..d5220d002574f25b199b5ac89a27f22a04a00df5 100644 (file)
--- a/lib/thread.c
+++ b/lib/thread.c
@@ -47,6 +47,9 @@ DEFINE_MTYPE_STATIC(LIB, THREAD_STATS, "Thread stats")
                write(m->io_pipe[1], &wakebyte, 1);                            \
        } while (0);
 
+/* max # of thread_fetch() calls before we force a poll() */
+#define MAX_TICK_IO 1000
+
 /* control variable for initializer */
 pthread_once_t init_once = PTHREAD_ONCE_INIT;
 pthread_key_t thread_current;
@@ -1355,30 +1358,42 @@ struct thread *thread_fetch(struct thread_master *m, struct thread *fetch)
                memcpy(m->handler.copy, m->handler.pfds,
                       m->handler.copycount * sizeof(struct pollfd));
 
-               pthread_mutex_unlock(&m->mtx);
-               {
-                       num = fd_poll(m, m->handler.copy, m->handler.pfdsize,
-                                     m->handler.copycount, tw);
-               }
-               pthread_mutex_lock(&m->mtx);
+               /*
+                * Attempt to flush ready queue before going into poll().
+                * This is performance-critical. Think twice before modifying.
+                */
+               if (m->ready.count == 0 || m->tick_since_io >= MAX_TICK_IO) {
+                       pthread_mutex_unlock(&m->mtx);
+                       {
+                               m->tick_since_io = 0;
+                               num = fd_poll(m, m->handler.copy,
+                                             m->handler.pfdsize,
+                                             m->handler.copycount, tw);
+                       }
+                       pthread_mutex_lock(&m->mtx);
+
+                       /* Handle any errors received in poll() */
+                       if (num < 0) {
+                               if (errno == EINTR) {
+                                       pthread_mutex_unlock(&m->mtx);
+                                       /* loop around to signal handler */
+                                       continue;
+                               }
 
-               /* Handle any errors received in poll() */
-               if (num < 0) {
-                       if (errno == EINTR) {
+                               /* else die */
+                               zlog_warn("poll() error: %s",
+                                         safe_strerror(errno));
                                pthread_mutex_unlock(&m->mtx);
-                               continue; /* loop around to signal handler */
+                               fetch = NULL;
+                               break;
                        }
 
-                       /* else die */
-                       zlog_warn("poll() error: %s", safe_strerror(errno));
-                       pthread_mutex_unlock(&m->mtx);
-                       fetch = NULL;
-                       break;
-               }
+                       /* Since we could have received more cancellation
+                        * requests during poll(), process those */
+                       do_thread_cancel(m);
 
-               /* Since we could have received more cancellation requests
-                * during poll(), process those */
-               do_thread_cancel(m);
+               } else
+                       m->tick_since_io++;
 
                /* Post timers to ready queue. */
                monotime(&now);

diff --git a/lib/thread.h b/lib/thread.h
index c830446e10209f4ead167c06729fae3d757eef41..86bf4df7c0c5facb96b091b86dc0de5de682799f 100644 (file)
--- a/lib/thread.h
+++ b/lib/thread.h
@@ -70,6 +70,7 @@ struct cancel_req {
 struct thread_master {
        char *name;
 
+       int tick_since_io;
        struct thread **read;
        struct thread **write;
        struct pqueue *timer;