[PATCH v2] Add --stats option to display event statistics

[Laurent Vivier <lvivier@redhat.com>]

Introduce a new --stats DELAY option that displays event statistics
tables showing counts by epoll event type. Statistics are printed to
stderr with a minimum delay between updates, and only when events occur.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 conf.c  |  8 ++++++++
 passt.1 |  5 +++++
 passt.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 passt.h |  2 ++
 4 files changed, 73 insertions(+)

diff --git a/conf.c b/conf.c
index 02e903b5cf70..66b9e63400ec 100644
--- a/conf.c
+++ b/conf.c
@@ -835,6 +835,8 @@ static void usage(const char *name, FILE *f, int status)
 		"\n"
 		"  -d, --debug		Be verbose\n"
 		"      --trace		Be extra verbose, implies --debug\n"
+		"  --stats DELAY  	Display events statistics\n"
+		"    minimum DELAY seconds between updates\n"
 		"  -q, --quiet		Don't print informational messages\n"
 		"  -f, --foreground	Don't run in background\n"
 		"    default: run in background\n"
@@ -1480,6 +1482,7 @@ void conf(struct ctx *c, int argc, char **argv)
 		{"repair-path",	required_argument,	NULL,		28 },
 		{"migrate-exit", no_argument,		NULL,		29 },
 		{"migrate-no-linger", no_argument,	NULL,		30 },
+		{"stats", required_argument,		NULL,		31 },
 		{ 0 },
 	};
 	const char *optstring = "+dqfel:hs:F:I:p:P:m:a:n:M:g:i:o:D:S:H:461t:u:T:U:";
@@ -1708,6 +1711,11 @@ void conf(struct ctx *c, int argc, char **argv)
 				die("--migrate-no-linger is for vhost-user mode only");
 			c->migrate_no_linger = true;
 
+			break;
+		case 31:
+			if (!c->foreground)
+				die("Can't display statistics if not running in foreground");
+			c->stats = strtol(optarg, NULL, 0);
 			break;
 		case 'd':
 			c->debug = 1;
diff --git a/passt.1 b/passt.1
index af5726a7f1c5..0c17454c3e43 100644
--- a/passt.1
+++ b/passt.1
@@ -84,6 +84,11 @@ Be verbose, don't log to the system logger.
 .BR \-\-trace
 Be extra verbose, show single packets. Implies \fB--debug\fR.
 
+.TP
+.BR \-\-stats " " \fIDELAY\fR
+Display events statistics with a minimum \fIDELAY\fR seconds between updates.
+If there is no event, statistics are not displayed.
+
 .TP
 .BR \-q ", " \-\-quiet
 Don't print informational messages.
diff --git a/passt.c b/passt.c
index a4ec115d1784..31fbb75b1b12 100644
--- a/passt.c
+++ b/passt.c
@@ -83,6 +83,14 @@ char *epoll_type_str[] = {
 static_assert(ARRAY_SIZE(epoll_type_str) == EPOLL_NUM_TYPES,
 	      "epoll_type_str[] doesn't match enum epoll_type");
 
+/**
+ * struct passt_stats - Statistics
+ * @events:	Event counters for epoll type events
+ */
+struct passt_stats {
+	unsigned long events[EPOLL_NUM_TYPES];
+};
+
 /**
  * post_handler() - Run periodic and deferred tasks for L4 protocol handlers
  * @c:		Execution context
@@ -174,6 +182,53 @@ static void exit_handler(int signal)
 	_exit(EXIT_SUCCESS);
 }
 
+/**
+ * print_stats() - Print event statistics table to stderr
+ * @c:		Execution context
+ * @stats:	Event counters
+ * @now:	Current timestamp
+ */
+static void print_stats(const struct ctx *c, const struct passt_stats *stats,
+			const struct timespec *now)
+{
+	static struct timespec before;
+	static int lines_printed;
+	long long elapsed_ns;
+	int i;
+
+	if (!c->stats)
+		return;
+
+	elapsed_ns = (now->tv_sec - before.tv_sec) * 1000000000LL +
+		     (now->tv_nsec - before.tv_nsec);
+
+	if (elapsed_ns < c->stats * 1000000000LL)
+		return;
+
+	before = *now;
+
+	if (!(lines_printed % 20)) {
+		/* Table header */
+		for (i = 1; i < EPOLL_NUM_TYPES; i++) {
+			int j;
+
+			for (j = 0; j < i * (6 + 1); j++) {
+				if (j && !(j % (6 + 1)))
+					FPRINTF(stderr, "|");
+				else
+					FPRINTF(stderr, " ");
+			}
+			FPRINTF(stderr, "%s\n", epoll_type_str[i]);
+		}
+	}
+
+	FPRINTF(stderr, " ");
+	for (i = 1; i < EPOLL_NUM_TYPES; i++)
+		FPRINTF(stderr, " %6lu", stats->events[i]);
+	FPRINTF(stderr, "\n");
+	lines_printed++;
+}
+
 /**
  * main() - Entry point and main loop
  * @argc:	Argument count
@@ -191,6 +246,7 @@ static void exit_handler(int signal)
 int main(int argc, char **argv)
 {
 	struct epoll_event events[EPOLL_EVENTS];
+	struct passt_stats stats = { 0 };
 	int nfds, i, devnull_fd = -1;
 	struct ctx c = { 0 };
 	struct rlimit limit;
@@ -362,6 +418,8 @@ loop:
 			/* Can't happen */
 			ASSERT(0);
 		}
+		stats.events[ref.type]++;
+		print_stats(&c, &stats, &now);
 	}
 
 	post_handler(&c, &now);
diff --git a/passt.h b/passt.h
index 3ffc19fdae05..0075eb4b3b16 100644
--- a/passt.h
+++ b/passt.h
@@ -187,6 +187,7 @@ struct ip6_ctx {
  * @mode:		Operation mode, qemu/UNIX domain socket or namespace/tap
  * @debug:		Enable debug mode
  * @trace:		Enable tracing (extra debug) mode
+ * @stats:		Events statistics delay (0 means disabled)
  * @quiet:		Don't print informational messages
  * @foreground:		Run in foreground, don't log to stderr by default
  * @nofile:		Maximum number of open files (ulimit -n)
@@ -248,6 +249,7 @@ struct ctx {
 	enum passt_modes mode;
 	int debug;
 	int trace;
+	int stats;
 	int quiet;
 	int foreground;
 	int nofile;
-- 
2.50.1