From 8313a31eba8d4535372c120a1c1683f8fcd1ede7 Mon Sep 17 00:00:00 2001
From: Joris Vink <joris@coders.se>
Date: Mon, 28 Jul 2014 23:27:58 +0200
Subject: [PATCH] If we do not own the accept lock, reduce timeout for platform
 wait.

This way multiple workers won't stall when passing the accept lock
around for at maximum 100 ms (time spent in epoll/kqueue waits).
---
 src/worker.c | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/src/worker.c b/src/worker.c
index df8d65c..6f27f42 100644
--- a/src/worker.c
+++ b/src/worker.c
@@ -55,7 +55,7 @@ static int	worker_trylock(void);
 static int	worker_unlock(void);
 static void	worker_decide_next(void);
 
-static void	kore_worker_acceptlock_obtain(void);
+static int	kore_worker_acceptlock_obtain(void);
 
 static TAILQ_HEAD(, connection)		disconnected;
 static TAILQ_HEAD(, connection)		worker_clients;
@@ -183,7 +183,7 @@ kore_worker_entry(struct kore_worker *kw)
 	int			quit;
 	char			buf[16];
 	struct connection	*c, *cnext;
-	u_int64_t		now, idle_check, last_cb_run;
+	u_int64_t		now, idle_check, last_cb_run, timer;
 
 	worker = kw;
 
@@ -250,10 +250,24 @@ kore_worker_entry(struct kore_worker *kw)
 			sig_recv = 0;
 		}
 
-		if (!worker->has_lock)
-			kore_worker_acceptlock_obtain();
+		/*
+		 * If we do not own the accept lock we want to reduce the time
+		 * spent waiting in kore_platform_event_wait() in case we get
+		 * handed the lock so we can grab it as fast as possible.
+		 *
+		 * Perhaps not the ideal thing to do, but I can't come up with
+		 * anything better right now.
+		 */
+		if (!worker->has_lock) {
+			if (kore_worker_acceptlock_obtain())
+				timer = 100;
+			else
+				timer = 1;
+		} else {
+			timer = 100;
+		}
 
-		kore_platform_event_wait();
+		kore_platform_event_wait(timer);
 
 		if (((worker->accepted >= worker->accept_treshold) ||
 		    (worker_active_connections >= worker_max_connections)) &&
@@ -418,15 +432,19 @@ kore_worker_acceptlock_release(void)
 	}
 }
 
-static void
+static int
 kore_worker_acceptlock_obtain(void)
 {
+	int		r;
+
 	if (worker_count == 1 && !worker->has_lock) {
 		worker->has_lock = 1;
 		kore_platform_enable_accept();
-		return;
+		return (1);
 	}
 
+	r = 0;
+
 	if (worker_trylock()) {
 		if (worker_active_connections >= worker_max_connections) {
 			worker->accepted = 0;
@@ -438,11 +456,14 @@ kore_worker_acceptlock_obtain(void)
 				worker->busy_warn = 1;
 			}
 		} else {
+			r = 1;
 			worker->has_lock = 1;
 			worker->busy_warn = 0;
 			kore_platform_enable_accept();
 		}
 	}
+
+	return (r);
 }
 
 static int