From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date: Sat, 26 Sep 2009 22:19:27 +0000 (-0400)
Subject: qsbr: adaptative usleep period
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=539718ae00831b55601635e6f065cb2aaf2aa7ae;p=urcu.git

qsbr: adaptative usleep period

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---

diff --git a/urcu-qsbr-static.h b/urcu-qsbr-static.h
index d18fabd..f1300f3 100644
--- a/urcu-qsbr-static.h
+++ b/urcu-qsbr-static.h
@@ -222,16 +222,16 @@ static inline void _rcu_read_unlock(void)
 static inline void _rcu_quiescent_state(void)
 {
 	long gp_ctr;
-	struct timeval current_time;
+	struct timeval current_time, delta_time;
 
 	smp_mb();
 	gettimeofday(&current_time, NULL);
-	if (current_time.tv_sec - urcu_reader_status.qs_time_last.tv_sec >= 1)
+	timersub(&current_time, &urcu_reader_status.qs_time_last, &delta_time);
+	if (delta_time.tv_sec >= 1)
 		_STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 1000000);
 	else
 		_STORE_SHARED(urcu_reader_status.qs_time_delta_usec,
-		      (unsigned long)current_time.tv_usec
-		      - (unsigned long)urcu_reader_status.qs_time_last.tv_usec);
+		      (unsigned long)delta_time.tv_usec);
 	urcu_reader_status.qs_time_last = current_time;
 	/*
 	 * volatile accesses can be reordered by the compiler when put in the
@@ -259,15 +259,15 @@ static inline void _rcu_thread_offline(void)
 
 static inline void _rcu_thread_online(void)
 {
-	struct timeval current_time;
+	struct timeval current_time, delta_time;
 
 	gettimeofday(&current_time, NULL);
-	if (current_time.tv_sec - urcu_reader_status.qs_time_last.tv_sec >= 1)
+	timersub(&current_time, &urcu_reader_status.qs_time_last, &delta_time);
+	if (delta_time.tv_sec >= 1)
 		_STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 1000000);
 	else
 		_STORE_SHARED(urcu_reader_status.qs_time_delta_usec,
-		      (unsigned long)current_time.tv_usec
-		      - (unsigned long)urcu_reader_status.qs_time_last.tv_usec);
+		      (unsigned long)delta_time.tv_usec);
 	urcu_reader_status.qs_time_last = current_time;
 	_STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 0);
 	_STORE_SHARED(urcu_reader_status.qs_gp, LOAD_SHARED(urcu_gp_ctr));
diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 5f06bfa..a71ee66 100644
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -119,7 +119,7 @@ static void wait_for_quiescent_state(void)
 		while (rcu_gp_ongoing(&index->urcu_reader_status->qs_gp)) {
 			if (wait_loops++ == RCU_QS_ACTIVE_ATTEMPTS) {
 				/* adapted wait time, in us */
-				usleep(LOAD_SHARED(index->urcu_reader_status->qs_time_delta_usec));
+				usleep(LOAD_SHARED(index->urcu_reader_status->qs_time_delta_usec) / 4);
 				wait_loops = 0;
 			} else {
 #ifndef HAS_INCOHERENT_CACHES