helper_thread: fix inconsistent status intervals

The signal handler safety changes to the helper thread have resulted in
inconsistent status-interval intervals. Consider the following:

$ ./fio-canonical/fio --name=test --rw=randwrite --ioengine=libaio --direct=1 --runtime=180 --time_based --filename=/dev/fioa --output=write-canonical.out --minimal --status-interval=1
$ cut -d ';' -f 50 < write-canonical.out | awk 'NR>1{print $1-p} {p=$1}' | sort -n | tail
1002
1002
1002
1002
1002
1042
1046
1251
1252
1252

Several of the status-interval output lines are ~1250ms apart.

This patch moves code for triggering the status-interval output from the main
fio process to the helper thread. The resulting intervals are much closer to
the desired 1000ms.

$ ./fio/fio --name=test --rw=randwrite --ioengine=libaio --direct=1 --runtime=180 --time_based --filename=/dev/fioa --minimal --status-interval=1 --output=write-test.out
$ cut -d ';' -f 50 < write-test.out | awk 'NR>1{print $1-p} {p=$1}' | sort -n | tail
1001
1001
1001
1001
1001
1001
1001
1001
1001
1001

Reported-by: <nate.rivers@wdc.com>
Fixes: 31eca64 ("Fix a potential deadlock in helper_do_stat()")
Signed-off-by: Vincent Fu <vincent.fu@wdc.com>

helper_thread.c

@@ -131,8 +131,9 @@ void helper_thread_exit(void)
 static void *helper_thread_main(void *data)
 {
 	struct helper_data *hd = data;
-	unsigned int msec_to_next_event, next_log, next_ss = STEADYSTATE_MSEC;
-	struct timespec ts, last_du, last_ss;
+	unsigned int msec_to_next_event, next_log, next_si;
+	unsigned int next_ss = STEADYSTATE_MSEC;
+	struct timespec ts, last_du, last_ss, last_si;
 	char action;
 	int ret = 0;
 
@@ -157,12 +158,13 @@ static void *helper_thread_main(void *data)
 #endif
 	memcpy(&last_du, &ts, sizeof(ts));
 	memcpy(&last_ss, &ts, sizeof(ts));
+	memcpy(&last_si, &ts, sizeof(ts));
 
 	fio_sem_up(hd->startup_sem);
 
 	msec_to_next_event = DISK_UTIL_MSEC;
 	while (!ret && !hd->exit) {
-		uint64_t since_du, since_ss = 0;
+		uint64_t since_du, since_si, since_ss = 0;
 		struct timeval timeout = {
 			.tv_sec  = msec_to_next_event / 1000,
 			.tv_usec = (msec_to_next_event % 1000) * 1000,
@@ -207,6 +209,20 @@ static void *helper_thread_main(void *data)
 		if (action == A_DO_STAT)
 			__show_running_run_stats();
 
+		if (status_interval) {
+			since_si = mtime_since(&last_si, &ts);
+			if (since_si >= status_interval || status_interval - since_si < 10) {
+				__show_running_run_stats();
+				timespec_add_msec(&last_si, since_si);
+				if (since_si > status_interval)
+					next_si = status_interval - (since_si - status_interval);
+				else
+					next_si = status_interval;
+			} else
+				next_si = status_interval - since_si;
+			msec_to_next_event = min(next_si, msec_to_next_event);
+		}
+
 		next_log = calc_log_samples();
 		if (!next_log)
 			next_log = DISK_UTIL_MSEC;

stat.c

@@ -2354,8 +2354,6 @@ void __show_running_run_stats(void)
 	fio_sem_up(stat_sem);
 }
 
-static bool status_interval_init;
-static struct timespec status_time;
 static bool status_file_disabled;
 
 #define FIO_STATUS_FILE		"fio-dump-status"
@@ -2398,16 +2396,6 @@ static int check_status_file(void)
 
 void check_for_running_stats(void)
 {
-	if (status_interval) {
-		if (!status_interval_init) {
-			fio_gettime(&status_time, NULL);
-			status_interval_init = true;
-		} else if (mtime_since_now(&status_time) >= status_interval) {
-			show_running_run_stats();
-			fio_gettime(&status_time, NULL);
-			return;
-		}
-	}
 	if (check_status_file()) {
 		show_running_run_stats();
 		return;