From 05ec9552a745f8a7f784e4796e4d364eb31d9f4a Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@openldap.org>
Date: Tue, 27 Jan 2009 08:00:50 +0000
Subject: [PATCH] Use epoll in edge-triggered mode

---
 servers/slapd/connection.c |  4 +--
 servers/slapd/daemon.c     | 52 +++++++++++++++++++++++++++++++++++---
 servers/slapd/proto-slap.h |  2 ++
 3 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/servers/slapd/connection.c b/servers/slapd/connection.c
index 9e2130d6de..ae781817ab 100644
--- a/servers/slapd/connection.c
+++ b/servers/slapd/connection.c
@@ -1240,7 +1240,7 @@ int connection_read_activate( ber_socket_t s )
 	 * thread reads data on it. Otherwise the listener thread will repeatedly
 	 * submit the same event on it to the pool.
 	 */
-	rc = slapd_clr_read( s, 0 );
+	rc = slapd_ack_read( s, 0 );
 	if ( rc )
 		return rc;
 
@@ -1844,7 +1844,7 @@ int connection_write(ber_socket_t s)
 
 	assert( connections != NULL );
 
-	slapd_clr_write( s, 0 );
+	slapd_ack_write( s, 0 );
 
 	c = connection_get( s );
 	if( c == NULL ) {
diff --git a/servers/slapd/daemon.c b/servers/slapd/daemon.c
index 31720d2d78..fb01e403f3 100644
--- a/servers/slapd/daemon.c
+++ b/servers/slapd/daemon.c
@@ -161,6 +161,9 @@ static struct slap_daemon {
 /***************************************
  * Use epoll infrastructure - epoll(4) *
  ***************************************/
+
+#undef SLAP_EVENT_ACK		/* events trigger once per descriptor */
+
 # define SLAP_EVENT_FNAME		"epoll"
 # define SLAP_EVENTS_ARE_INDEXED	0
 # define SLAP_EPOLL_SOCK_IX(s)		(slap_daemon.sd_index[(s)])
@@ -215,7 +218,7 @@ static struct slap_daemon {
 	int rc; \
 	SLAP_EPOLL_SOCK_IX((s)) = slap_daemon.sd_nfds; \
 	SLAP_EPOLL_SOCK_EP((s)).data.ptr = (l) ? (l) : (void *)(&SLAP_EPOLL_SOCK_IX(s)); \
-	SLAP_EPOLL_SOCK_EV((s)) = EPOLLIN; \
+	SLAP_EPOLL_SOCK_EV((s)) = EPOLLIN|EPOLLET; \
 	rc = epoll_ctl(slap_daemon.sd_epfd, EPOLL_CTL_ADD, \
 		(s), &SLAP_EPOLL_SOCK_EP((s))); \
 	if ( rc == 0 ) { \
@@ -291,10 +294,12 @@ static struct slap_daemon {
 } while (0)
 
 #elif defined(SLAP_X_DEVPOLL) && defined(HAVE_DEVPOLL)
-
 /*************************************************************
  * Use Solaris' (>= 2.7) /dev/poll infrastructure - poll(7d) *
  *************************************************************/
+
+#define SLAP_EVENT_ACK	1	/* events keep signalling unless we stop them */
+
 # define SLAP_EVENT_FNAME		"/dev/poll"
 # define SLAP_EVENTS_ARE_INDEXED	0
 /*
@@ -470,6 +475,9 @@ static struct slap_daemon {
 } while (0)
 
 #else /* ! epoll && ! /dev/poll */
+
+#define SLAP_EVENT_ACK	1	/* events keep signalling unless we stop them */
+
 # ifdef HAVE_WINSOCK
 # define SLAP_EVENT_FNAME		"WSselect"
 /* Winsock provides a "select" function but its fd_sets are
@@ -927,6 +935,24 @@ slapd_remove(
 	WAKE_LISTENER(wake || slapd_gentle_shutdown == 2);
 }
 
+void
+slapd_ack_write( ber_socket_t s, int wake )
+{
+#ifdef SLAP_EVENT_ACK
+	ldap_pvt_thread_mutex_lock( &slap_daemon.sd_mutex );
+
+	if ( SLAP_SOCK_IS_WRITE( s )) {
+		assert( SLAP_SOCK_IS_ACTIVE( s ));
+
+		SLAP_SOCK_CLR_WRITE( s );
+		slap_daemon.sd_nwriters--;
+	}
+
+	ldap_pvt_thread_mutex_unlock( &slap_daemon.sd_mutex );
+#endif
+	WAKE_LISTENER(wake);
+}
+
 void
 slapd_clr_write( ber_socket_t s, int wake )
 {
@@ -959,6 +985,26 @@ slapd_set_write( ber_socket_t s, int wake )
 	WAKE_LISTENER(wake);
 }
 
+int
+slapd_ack_read( ber_socket_t s, int wake )
+{
+#ifdef SLAP_EVENT_ACK
+	int rc = 1;
+	ldap_pvt_thread_mutex_lock( &slap_daemon.sd_mutex );
+
+	if ( SLAP_SOCK_IS_ACTIVE( s )) {
+		SLAP_SOCK_CLR_READ( s );
+		rc = 0;
+	}
+	ldap_pvt_thread_mutex_unlock( &slap_daemon.sd_mutex );
+	if ( !rc )
+		WAKE_LISTENER(wake);
+	return rc;
+#else
+	return 0;
+#endif
+}
+
 int
 slapd_clr_read( ber_socket_t s, int wake )
 {
@@ -2513,7 +2559,7 @@ slapd_daemon_task(
 					char c[BUFSIZ];
 					waking = 0;
 					tcp_read( SLAP_FD2SOCK(wake_sds[0]), c, sizeof(c) );
-					break;
+					continue;
 				}
 
 				if ( SLAP_EVENT_IS_WRITE( i ) ) {
diff --git a/servers/slapd/proto-slap.h b/servers/slapd/proto-slap.h
index 5837bb50f2..3bfe126370 100644
--- a/servers/slapd/proto-slap.h
+++ b/servers/slapd/proto-slap.h
@@ -831,8 +831,10 @@ LDAP_SLAPD_F (void) slap_wake_listener LDAP_P((void));
 
 LDAP_SLAPD_F (void) slapd_set_write LDAP_P((ber_socket_t s, int wake));
 LDAP_SLAPD_F (void) slapd_clr_write LDAP_P((ber_socket_t s, int wake));
+LDAP_SLAPD_F (void) slapd_ack_write LDAP_P((ber_socket_t s, int wake));
 LDAP_SLAPD_F (void) slapd_set_read LDAP_P((ber_socket_t s, int wake));
 LDAP_SLAPD_F (int) slapd_clr_read LDAP_P((ber_socket_t s, int wake));
+LDAP_SLAPD_F (int) slapd_ack_read LDAP_P((ber_socket_t s, int wake));
 
 LDAP_SLAPD_V (volatile sig_atomic_t) slapd_abrupt_shutdown;
 LDAP_SLAPD_V (volatile sig_atomic_t) slapd_shutdown;
-- 
2.39.5