[MEDIUM] poll: add a measurement of idle vs work time

We now measure the work and idle times in order to report the idle
time in the stats. It's expected that we'll be able to use it at
other places later.
diff --git a/include/common/time.h b/include/common/time.h
index abc1ccf..14ca589 100644
--- a/include/common/time.h
+++ b/include/common/time.h
@@ -1,23 +1,23 @@
 /*
-  include/common/time.h
-  Time calculation functions and macros.
-
-  Copyright (C) 2000-2008 Willy Tarreau - w@1wt.eu
-  
-  This library is free software; you can redistribute it and/or
-  modify it under the terms of the GNU Lesser General Public
-  License as published by the Free Software Foundation, version 2.1
-  exclusively.
-
-  This library is distributed in the hope that it will be useful,
-  but WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-  Lesser General Public License for more details.
-
-  You should have received a copy of the GNU Lesser General Public
-  License along with this library; if not, write to the Free Software
-  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
-*/
+ * include/common/time.h
+ * Time calculation functions and macros.
+ *
+ * Copyright (C) 2000-2011 Willy Tarreau - w@1wt.eu
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
 
 #ifndef _COMMON_TIME_H
 #define _COMMON_TIME_H
@@ -57,9 +57,14 @@
 extern unsigned int   curr_sec_ms;      /* millisecond of current second (0..999) */
 extern unsigned int   curr_sec_ms_scaled;  /* millisecond of current second (0..2^32-1) */
 extern unsigned int   now_ms;           /* internal date in milliseconds (may wrap) */
+extern unsigned int   samp_time;        /* total elapsed time over current sample */
+extern unsigned int   idle_time;        /* total idle time over current sample */
+extern unsigned int   idle_pct;         /* idle to total ratio over last sample (percent) */
 extern struct timeval now;              /* internal date is a monotonic function of real clock */
 extern struct timeval date;             /* the real current date */
 extern struct timeval start_date;       /* the process's start date */
+extern struct timeval before_poll;      /* system date before calling poll() */
+extern struct timeval after_poll;       /* system date after leaving poll() */
 
 
 /**** exported functions *************************************************/
@@ -516,6 +521,35 @@
 
 char *human_time(int t, short hz_div);
 
+/* Update the idle time value twice a second, to be called after
+ * tv_update_date() when called after poll(). It relies on <before_poll> to be
+ * updated to the system time before calling poll().
+ */
+static inline void measure_idle()
+{
+	/* Let's compute the idle to work ratio. We worked between after_poll
+	 * and before_poll, and slept between before_poll and date. The idle_pct
+	 * is updated at most twice every second. Note that the current second
+	 * rarely changes so we avoid a multiply when not needed.
+	 */
+	int delta;
+
+	if ((delta = date.tv_sec - before_poll.tv_sec))
+		delta *= 1000000;
+	idle_time += delta + (date.tv_usec - before_poll.tv_usec);
+
+	if ((delta = date.tv_sec - after_poll.tv_sec))
+		delta *= 1000000;
+	samp_time += delta + (date.tv_usec - after_poll.tv_usec);
+
+	after_poll.tv_sec = date.tv_sec; after_poll.tv_usec = date.tv_usec;
+	if (samp_time < 500000)
+		return;
+
+	idle_pct = (100 * idle_time + samp_time / 2) / samp_time;
+	idle_time = samp_time = 0;
+}
+
 #endif /* _COMMON_TIME_H */
 
 /*
diff --git a/src/dumpstats.c b/src/dumpstats.c
index 5dcd8c4..ebfb179 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -1605,6 +1605,7 @@
 				     "MaxConnRate: %d\n"
 				     "Tasks: %d\n"
 				     "Run_queue: %d\n"
+				     "Idle_pct: %d\n"
 				     "node: %s\n"
 				     "description: %s\n"
 				     "",
@@ -1618,7 +1619,7 @@
 				     global.maxsock, global.maxconn, global.hardmaxconn, global.maxpipes,
 				     actconn, pipes_used, pipes_free,
 				     read_freq_ctr(&global.conn_per_sec), global.cps_lim, global.cps_max,
-				     nb_tasks_cur, run_queue_cur,
+				     nb_tasks_cur, run_queue_cur, idle_pct,
 				     global.node, global.desc?global.desc:""
 				     );
 			if (buffer_feed_chunk(si->ib, &msg) >= 0)
@@ -1934,7 +1935,7 @@
 			     "<b>system limits:</b> memmax = %s%s; ulimit-n = %d<br>\n"
 			     "<b>maxsock = </b> %d; <b>maxconn = </b> %d; <b>maxpipes = </b> %d<br>\n"
 			     "current conns = %d; current pipes = %d/%d; conn rate = %d/sec<br>\n"
-			     "Running tasks: %d/%d<br>\n"
+			     "Running tasks: %d/%d; idle = %d %%<br>\n"
 			     "</td><td align=\"center\" nowrap>\n"
 			     "<table class=\"lgd\"><tr>\n"
 			     "<td class=\"active3\">&nbsp;</td><td class=\"noborder\">active UP </td>"
@@ -1967,7 +1968,7 @@
 			     global.rlimit_nofile,
 			     global.maxsock, global.maxconn, global.maxpipes,
 			     actconn, pipes_used, pipes_used+pipes_free, read_freq_ctr(&global.conn_per_sec),
-			     run_queue_cur, nb_tasks_cur
+			     run_queue_cur, nb_tasks_cur, idle_pct
 			     );
 
 			if (si->applet.ctx.stats.flags & STAT_HIDE_DOWN)
diff --git a/src/ev_epoll.c b/src/ev_epoll.c
index 958c4e6..bc7493b 100644
--- a/src/ev_epoll.c
+++ b/src/ev_epoll.c
@@ -236,8 +236,10 @@
 	}
 
 	fd = MIN(maxfd, global.tune.maxpollevents);
+	gettimeofday(&before_poll, NULL);
 	status = epoll_wait(epoll_fd, epoll_events, fd, wait_time);
 	tv_update_date(wait_time, status);
+	measure_idle();
 
 	for (count = 0; count < status; count++) {
 		fd = epoll_events[count].data.fd;
diff --git a/src/ev_kqueue.c b/src/ev_kqueue.c
index e167984..b43533a 100644
--- a/src/ev_kqueue.c
+++ b/src/ev_kqueue.c
@@ -126,6 +126,7 @@
 	}
 
 	fd = MIN(maxfd, global.tune.maxpollevents);
+	gettimeofday(&before_poll, NULL);
 	status = kevent(kqueue_fd, // int kq
 			NULL,      // const struct kevent *changelist
 			0,         // int nchanges
@@ -133,6 +134,7 @@
 			fd,        // int nevents
 			&timeout); // const struct timespec *timeout
 	tv_update_date(delta_ms, status);
+	measure_idle();
 
 	for (count = 0; count < status; count++) {
 		fd = kev[count].ident;
diff --git a/src/ev_poll.c b/src/ev_poll.c
index f5d011e..ec18863 100644
--- a/src/ev_poll.c
+++ b/src/ev_poll.c
@@ -137,8 +137,10 @@
 			wait_time = MAX_DELAY_MS;
 	}
 
+	gettimeofday(&before_poll, NULL);
 	status = poll(poll_events, nbfd, wait_time);
 	tv_update_date(wait_time, status);
+	measure_idle();
 
 	for (count = 0; status > 0 && count < nbfd; count++) {
 		fd = poll_events[count].fd;
diff --git a/src/ev_select.c b/src/ev_select.c
index 5a87282..0924e3f 100644
--- a/src/ev_select.c
+++ b/src/ev_select.c
@@ -125,6 +125,7 @@
 	//	    
 	//	}
 
+	gettimeofday(&before_poll, NULL);
 	status = select(maxfd,
 			readnotnull ? tmp_evts[DIR_RD] : NULL,
 			writenotnull ? tmp_evts[DIR_WR] : NULL,
@@ -132,6 +133,7 @@
 			&delta);
       
 	tv_update_date(delta_ms, status);
+	measure_idle();
 
 	if (status <= 0)
 		return;
diff --git a/src/ev_sepoll.c b/src/ev_sepoll.c
index c9c5978..a7fb64c 100644
--- a/src/ev_sepoll.c
+++ b/src/ev_sepoll.c
@@ -475,8 +475,10 @@
 	/* we want to detect if an accept() will create new speculative FDs here */
 	fd_created = 0;
 	spec_processed = 0;
+	gettimeofday(&before_poll, NULL);
 	status = epoll_wait(epoll_fd, epoll_events, fd, wait_time);
 	tv_update_date(wait_time, status);
+	measure_idle();
 
 	for (count = 0; count < status; count++) {
 		int e = epoll_events[count].events;
diff --git a/src/time.c b/src/time.c
index 1b0f72c..4c41239 100644
--- a/src/time.c
+++ b/src/time.c
@@ -1,7 +1,7 @@
 /*
  * Time calculation functions.
  *
- * Copyright 2000-2009 Willy Tarreau <w@1wt.eu>
+ * Copyright 2000-2011 Willy Tarreau <w@1wt.eu>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -19,9 +19,14 @@
 unsigned int   curr_sec_ms;      /* millisecond of current second (0..999) */
 unsigned int   curr_sec_ms_scaled;  /* millisecond of current second (0..2^32-1) */
 unsigned int   now_ms;          /* internal date in milliseconds (may wrap) */
+unsigned int   samp_time;       /* total elapsed time over current sample */
+unsigned int   idle_time;       /* total idle time over current sample */
+unsigned int   idle_pct;        /* idle to total ratio over last sample (percent) */
 struct timeval now;             /* internal date is a monotonic function of real clock */
 struct timeval date;            /* the real current date */
 struct timeval start_date;      /* the process's start date */
+struct timeval before_poll;     /* system date before calling poll() */
+struct timeval after_poll;      /* system date after leaving poll() */
 
 /*
  * adds <ms> ms to <from>, set the result to <tv> and returns a pointer <tv>
@@ -165,6 +170,9 @@
 	if (unlikely(max_wait < 0)) {
 		tv_zero(&tv_offset);
 		adjusted = date;
+		after_poll = date;
+		samp_time = idle_time = 0;
+		idle_pct = 100;
 		goto to_ms;
 	}
 	__tv_add(&adjusted, &date, &tv_offset);