From bfdf56c22e9b8d30d08bf3b59b68fd2993f0c4ca Mon Sep 17 00:00:00 2001
From: Niels Provos <provos@gmail.com>
Date: Sat, 3 May 2008 18:27:24 +0000
Subject: [PATCH] from trunk: cache clock_gettime/gettimeofday values in base

svn:r759
---
 ChangeLog        |  1 +
 event-internal.h |  2 ++
 event.c          | 46 +++++++++++++++++++++++++++++-----------------
 3 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 0f3f1e8b..442d1a25 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,6 +7,7 @@ Changes in 1.4.4-stable:
  o fix a bug in bufferevent read water marks and add a test for them
  o introduce bufferevent_setcb and bufferevent_setfd to allow better manipulation of bufferevents
  o use libevent's internal timercmp on all platforms, to avoid bugs on old platforms where timercmp(a,b,<=) is buggy.
+ o reduce system calls for getting current time by caching it.
 
 
 Changes in 1.4.3-stable:
diff --git a/event-internal.h b/event-internal.h
index 19b7a547..7485f217 100644
--- a/event-internal.h
+++ b/event-internal.h
@@ -66,6 +66,8 @@ struct event_base {
 	struct timeval event_tv;
 
 	struct min_heap timeheap;
+
+	struct timeval tv_cache;
 };
 
 /* Internal use only: Functions that might be missing from <sys/queue.h> */
diff --git a/event.c b/event.c
index e96c1b6a..5efaaee0 100644
--- a/event.c
+++ b/event.c
@@ -137,8 +137,13 @@ detect_monotonic(void)
 }
 
 static int
-gettime(struct timeval *tp)
+gettime(struct event_base *base, struct timeval *tp)
 {
+	if (base->tv_cache.tv_sec) {
+		*tp = base->tv_cache;
+		return (0);
+	}
+
 #if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
 	struct timespec	ts;
 
@@ -179,7 +184,7 @@ event_base_new(void)
 	event_gotsig = 0;
 
 	detect_monotonic();
-	gettime(&base->event_tv);
+	gettime(base, &base->event_tv);
 	
 	min_heap_ctor(&base->timeheap);
 	TAILQ_INIT(&base->eventqueue);
@@ -497,10 +502,17 @@ event_base_loop(struct event_base *base, int flags)
 			return (1);
 		}
 
+		/* update last old time */
+		gettime(base, &base->event_tv);
+
+		/* clear time cache */
+		base->tv_cache.tv_sec = 0;
+
 		res = evsel->dispatch(base, evbase, tv_p);
 
 		if (res == -1)
 			return (-1);
+		gettime(base, &base->tv_cache);
 
 		timeout_process(base);
 
@@ -668,7 +680,7 @@ event_pending(struct event *ev, short event, struct timeval *tv)
 
 	/* See if there is a timeout that we should report */
 	if (tv != NULL && (flags & event & EV_TIMEOUT)) {
-		gettime(&now);
+		gettime(ev->ev_base, &now);
 		evutil_timersub(&ev->ev_timeout, &now, &res);
 		/* correctly remap to real time */
 		gettimeofday(&now, NULL);
@@ -720,7 +732,7 @@ event_add(struct event *ev, struct timeval *tv)
 			event_queue_remove(base, ev, EVLIST_ACTIVE);
 		}
 
-		gettime(&now);
+		gettime(base, &now);
 		evutil_timeradd(&now, tv, &ev->ev_timeout);
 
 		event_debug((
@@ -820,7 +832,7 @@ timeout_next(struct event_base *base, struct timeval **tv_p)
 		return (0);
 	}
 
-	if (gettime(&now) == -1)
+	if (gettime(base, &now) == -1)
 		return (-1);
 
 	if (evutil_timercmp(&ev->ev_timeout, &now, <=)) {
@@ -854,7 +866,7 @@ timeout_correct(struct event_base *base, struct timeval *tv)
 		return;
 
 	/* Check if time is running backwards */
-	gettime(tv);
+	gettime(base, tv);
 	if (evutil_timercmp(tv, &base->event_tv, >=)) {
 		base->event_tv = *tv;
 		return;
@@ -885,7 +897,7 @@ timeout_process(struct event_base *base)
 	if (min_heap_empty(&base->timeheap))
 		return;
 
-	gettime(&now);
+	gettime(base, &now);
 
 	while ((ev = min_heap_top(&base->timeheap))) {
 		if (evutil_timercmp(&ev->ev_timeout, &now, >))
@@ -912,19 +924,19 @@ event_queue_remove(struct event_base *base, struct event *ev, int queue)
 
 	ev->ev_flags &= ~queue;
 	switch (queue) {
+	case EVLIST_INSERTED:
+		TAILQ_REMOVE(&base->eventqueue, ev, ev_next);
+		break;
 	case EVLIST_ACTIVE:
 		base->event_count_active--;
 		TAILQ_REMOVE(base->activequeues[ev->ev_pri],
 		    ev, ev_active_next);
 		break;
-	case EVLIST_SIGNAL:
-		TAILQ_REMOVE(&base->sig.signalqueue, ev, ev_signal_next);
-		break;
 	case EVLIST_TIMEOUT:
 		min_heap_erase(&base->timeheap, ev);
 		break;
-	case EVLIST_INSERTED:
-		TAILQ_REMOVE(&base->eventqueue, ev, ev_next);
+	case EVLIST_SIGNAL:
+		TAILQ_REMOVE(&base->sig.signalqueue, ev, ev_signal_next);
 		break;
 	default:
 		event_errx(1, "%s: unknown queue %x", __func__, queue);
@@ -948,20 +960,20 @@ event_queue_insert(struct event_base *base, struct event *ev, int queue)
 
 	ev->ev_flags |= queue;
 	switch (queue) {
+	case EVLIST_INSERTED:
+		TAILQ_INSERT_TAIL(&base->eventqueue, ev, ev_next);
+		break;
 	case EVLIST_ACTIVE:
 		base->event_count_active++;
 		TAILQ_INSERT_TAIL(base->activequeues[ev->ev_pri],
 		    ev,ev_active_next);
 		break;
-	case EVLIST_SIGNAL:
-		TAILQ_INSERT_TAIL(&base->sig.signalqueue, ev, ev_signal_next);
-		break;
 	case EVLIST_TIMEOUT: {
 		min_heap_push(&base->timeheap, ev);
 		break;
 	}
-	case EVLIST_INSERTED:
-		TAILQ_INSERT_TAIL(&base->eventqueue, ev, ev_next);
+	case EVLIST_SIGNAL:
+		TAILQ_INSERT_TAIL(&base->sig.signalqueue, ev, ev_signal_next);
 		break;
 	default:
 		event_errx(1, "%s: unknown queue %x", __func__, queue);