From: Willy Tarreau <w@1wt.eu>
Date: Sat, 9 Jul 2022 21:38:46 +0000 (+0200)
Subject: MEDIUM: poller: disable thread-groups for poll() and select()
X-Git-Tag: v2.7-dev2~37
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e5715bfacec7ce312bb6a297c534e8bbed2f8025;p=thirdparty%2Fhaproxy.git

MEDIUM: poller: disable thread-groups for poll() and select()

These old legacy pollers are not designed for this. They're still
using a shared list of events for all threads, this will not scale at
all, so there's no point in enabling thread-groups there. Modern
systems have epoll, kqueue or event ports and do not need these ones.

We arrange for failing at boot time, only when thread-groups > 1 so
that existing setups will remain unaffected.

If there's a compelling reason for supporting thread groups with these
pollers in the future, the rework should not be too hard, it would just
consume a lot of memory to have an fd_evts[] array per thread, but that
is doable.
---

diff --git a/src/ev_poll.c b/src/ev_poll.c
index 3cc41dc687..b25d1dc328 100644
--- a/src/ev_poll.c
+++ b/src/ev_poll.c
@@ -264,6 +264,13 @@ static int _do_init(struct poller *p)
 	int fd_evts_bytes;
 
 	p->private = NULL;
+
+	/* this old poller uses a process-wide FD list that cannot work with
+	 * groups.
+	 */
+	if (global.nbtgroups > 1)
+		goto fail_srevt;
+
 	fd_evts_bytes = (global.maxsock + sizeof(**fd_evts) * 8 - 1) / (sizeof(**fd_evts) * 8) * sizeof(**fd_evts);
 
 	if ((fd_evts[DIR_RD] = calloc(1, fd_evts_bytes)) == NULL)
diff --git a/src/ev_select.c b/src/ev_select.c
index b3e1b40e6e..af14b2e9e7 100644
--- a/src/ev_select.c
+++ b/src/ev_select.c
@@ -247,6 +247,12 @@ static int _do_init(struct poller *p)
 
 	p->private = NULL;
 
+	/* this old poller uses a process-wide FD list that cannot work with
+	 * groups.
+	 */
+	if (global.nbtgroups > 1)
+		goto fail_srevt;
+
 	if (global.maxsock > FD_SETSIZE)
 		goto fail_srevt;
 
diff --git a/src/haproxy.c b/src/haproxy.c
index 513a967f20..3f03826a6d 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -2533,7 +2533,8 @@ static void init(int argc, char **argv)
 
 	if (!init_pollers()) {
 		ha_alert("No polling mechanism available.\n"
-			 "  It is likely that haproxy was built with TARGET=generic and that FD_SETSIZE\n"
+			 "  This may happen when using thread-groups with old pollers (poll/select), or\n"
+			 "  it is possible that haproxy was built with TARGET=generic and that FD_SETSIZE\n"
 			 "  is too low on this platform to support maxconn and the number of listeners\n"
 			 "  and servers. You should rebuild haproxy specifying your system using TARGET=\n"
 			 "  in order to support other polling systems (poll, epoll, kqueue) or reduce the\n"