Improve QPS calculation

src/gc.c

@@ -504,6 +504,7 @@ void *GC_thread(void *val)
 	while(!killed)
 	{
 		const time_t now = time(NULL);
+		const double time_start = double_time();
 		if(config.dns.rateLimit.interval.v.ui > 0 &&
 		   (unsigned int)(now - lastRateLimitCleaner) >= config.dns.rateLimit.interval.v.ui)
 		{
@@ -560,7 +561,26 @@ void *GC_thread(void *val)
 			reread_config();
 		}
 
-		thread_sleepms(GC, 1000);
+		// Intermediate cancellation-point
+		if(killed)
+			break;
+
+		// Reset the queries-per-second counter
+		lock_shm();
+		reset_qps(now);
+		unlock_shm();
+
+		// Intermediate cancellation-point
+		if(killed)
+			break;
+
+		// Sleep for the remaining time of the interval (if any)
+		const double time_end = double_time();
+		const double time_diff = time_end - time_start;
+		const double sleep_time = 1.0 - time_diff; // 1.0 second interval
+
+		if(sleep_time > 0)
+			thread_sleepms(GC, (unsigned int)(sleep_time*1000));
 	}
 
 	// Close inotify watcher

src/shmem.c

@@ -1210,29 +1210,23 @@ int __attribute__((pure)) is_shm_fd(const int fd)
 // Update queries per second (qps) value
 // This is done in shared memory to allow for both UDP and TCP workers to
 // contribute.
-void update_qps(const double timestamp)
+void update_qps(const time_t timestamp)
 {
 	// Get the timeslot for the current timestamp
-	const unsigned int slot = (unsigned int)timestamp % QPS_AVGLEN;
+	const unsigned int slot = timestamp % QPS_AVGLEN;
 
-	// Check if the timestamp is in the same slot as the last one
-	if(shmSettings->qps.last != slot)
-	{
-		// Reset all the slots in between
-		// This is relevant if less than one query per second is
-		// received and the intermediate slots are not updated
-		for(unsigned int i = (shmSettings->qps.last + 1) % QPS_AVGLEN; i != slot; i = (i + 1) % QPS_AVGLEN)
-			shmSettings->qps.buf[i] = 0;
-
-		// Reset the current slot
-		shmSettings->qps.buf[slot] = 0;
+	// Add the query
+	shmSettings->qps[slot]++;
+}
 
-		// Update the last slot index
-		shmSettings->qps.last = slot;
-	}
+// Reset queries per second (qps) value for a given timeslot
+void reset_qps(const time_t timestamp)
+{
+	// Get the timeslot for the current timestamp
+	const unsigned int slot = timestamp % QPS_AVGLEN;
 
-	// Add the query
-	shmSettings->qps.buf[slot]++;
+	// Reset the query count
+	shmSettings->qps[slot] = 0;
 }
 
 // Compute queries per second (qps) value
@@ -1245,7 +1239,7 @@ double __attribute__((pure)) get_qps(void)
 	//
 	double qps = 0.0;
 	for(unsigned int i = 0; i < QPS_AVGLEN; i++)
-		qps += shmSettings->qps.buf[i];
+		qps += shmSettings->qps[i];
 
 	return qps / QPS_AVGLEN;
 }

src/shmem.h

@@ -31,10 +31,7 @@ typedef struct {
 	pid_t pid;
 	unsigned int global_shm_counter;
 	unsigned int next_str_pos;
-	struct {
-		unsigned int last;
-		unsigned int buf[QPS_AVGLEN];
-	} qps;
+	unsigned int qps[QPS_AVGLEN];
 } ShmSettings;
 
 typedef struct {
@@ -155,7 +152,8 @@ void set_per_client_regex(const int clientID, const int regexID, const bool valu
 // Used in dnsmasq/utils.c
 int is_shm_fd(const int fd);
 
-void update_qps(const double timestamp);
+void update_qps(const time_t timestamp);
+void reset_qps(const time_t timestamp);
 double get_qps(void) __attribute__((pure));
 
 #endif //SHARED_MEMORY_SERVER_H