[OPTIM] introduce global parameter "tune.maxaccept"

This new parameter makes it possible to override the default
number of consecutive incoming connections which can be
accepted on a socket. By default it is not limited on single
process mode, and limited to 8 in multi-process mode.

doc/configuration.txt

@@ -67,8 +67,9 @@ The following keywords are supported in the "global" section :
    - nokqueue
    - nopoll
    - nosepoll
-   - tune.maxpollevents
    - spread-checks
+   - tune.maxaccept
+   - tune.maxpollevents
   
  * Debugging
    - debug
@@ -212,13 +213,6 @@ nosepoll
   is equivalent to the command-line argument "-ds". The next polling system
   used will generally be "epoll". See also "nosepoll", and "nopoll".
 
-tune.maxpollevents <number>
-  Sets the maximum amount of events that can be processed at once in a call to
-  the polling system. The default value is adapted to the operating system. It
-  has been noticed that reducing it below 200 tends to slightly decrease
-  latency at the expense of network bandwidth, and increasing it above 200
-  tends to trade latency for slightly increased bandwidth.
-
 spread-checks <0..50, in percent>
   Sometimes it is desirable to avoid sending health checks to servers at exact
   intervals, for instance when many logical servers are located on the same
@@ -226,6 +220,23 @@ spread-checks <0..50, in percent>
   some randomness in the check interval between 0 and +/- 50%. A value between
   2 and 5 seems to show good results. The default value remains at 0.
 
+tune.maxaccept <number>
+  Sets the maximum number of consecutive accepts that a process may perform on
+  a single wake up. High values give higher priority to high connection rates,
+  while lower values give higher priority to already established connections.
+  This value is unlimited by default in single process mode. However, in
+  multi-process mode (nbproc > 1), it defaults to 8 so that when one process
+  wakes up, it does not take all incoming connections for itself and leaves a
+  part of them to other processes. Setting this value to zero or less disables
+  the limitation. It should normally not be needed to tweak this value.
+
+tune.maxpollevents <number>
+  Sets the maximum amount of events that can be processed at once in a call to
+  the polling system. The default value is adapted to the operating system. It
+  has been noticed that reducing it below 200 tends to slightly decrease
+  latency at the expense of network bandwidth, and increasing it above 200
+  tends to trade latency for slightly increased bandwidth.
+
 
 1.3) Debugging
 ---------------

include/types/global.h

@@ -63,6 +63,7 @@ struct global {
 	struct logsrv logsrv1, logsrv2;
 	struct {
 		int maxpollevents; /* max number of poll events at once */
+		int maxaccept;     /* max number of consecutive accept() */
 	} tune;
 	struct listener stats_sock; /* unix socket listener for statistics */
 	struct timeval stats_timeout;

src/cfgparse.c

@@ -307,6 +307,17 @@ int cfg_parse_global(const char *file, int linenum, char **args, int inv)
 		}
 		global.tune.maxpollevents = atol(args[1]);
 	}
+	else if (!strcmp(args[0], "tune.maxaccept")) {
+		if (global.tune.maxaccept != 0) {
+			Alert("parsing [%s:%d] : '%s' already specified. Continuing.\n", file, linenum, args[0]);
+			return 0;
+		}
+		if (*(args[1]) == 0) {
+			Alert("parsing [%s:%d] : '%s' expects an integer argument.\n", file, linenum, args[0]);
+			return -1;
+		}
+		global.tune.maxaccept = atol(args[1]);
+	}
 	else if (!strcmp(args[0], "uid")) {
 		if (global.uid != 0) {
 			Alert("parsing [%s:%d] : user/uid already specified. Continuing.\n", file, linenum);

src/client.c

@@ -74,12 +74,7 @@ int event_accept(int fd) {
 	struct http_txn *txn;
 	struct task *t;
 	int cfd;
-	int max_accept;
-
-	if (global.nbproc > 1)
-		max_accept = 8; /* let other processes catch some connections too */
-	else
-		max_accept = -1;
+	int max_accept = global.tune.maxaccept;
 
 	while (p->feconn < p->maxconn && max_accept--) {
 		struct sockaddr_storage addr;

src/haproxy.c

@@ -569,6 +569,13 @@ void init(int argc, char **argv)
 	if (global.tune.maxpollevents <= 0)
 		global.tune.maxpollevents = MAX_POLL_EVENTS;
 
+	if (global.tune.maxaccept <= 0) {
+		if (global.nbproc > 1)
+			global.tune.maxaccept = 8;  /* leave some conns to other processes */
+		else
+			global.tune.maxaccept = -1; /* accept all incoming conns */
+	}
+
 	if (arg_mode & (MODE_DEBUG | MODE_FOREGROUND)) {
 		/* command line debug mode inhibits configuration mode */
 		global.mode &= ~(MODE_DAEMON | MODE_QUIET);