From: Willy Tarreau <w@1wt.eu>
Date: Fri, 30 Jul 2021 11:55:36 +0000 (+0200)
Subject: BUG/MINOR: select: fix excess number of dead/skip reported
X-Git-Tag: v2.5-dev3~13
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=fcc5281513eabe0d7790d98e50ee8cd9be216c1b;p=thirdparty%2Fhaproxy.git

BUG/MINOR: select: fix excess number of dead/skip reported

In 1.8, commit ab62f5195 ("MINOR: polling: Use fd_update_events to update
events seen for a fd") updated the pollers to rely on fd_update_events(),
but the modification delayed the test of presence of the FD in the report,
resulting in owner/thread_mask and possibly event updates being performed
for each FD appearing in a block of 32 FDs around an active one. This
caused the request rate to be ~3 times lower with select() than poll()
under 6 threads.

This can be backported as far as 1.8.
---

diff --git a/src/ev_select.c b/src/ev_select.c
index ab5da35b7c..3e5ee5a252 100644
--- a/src/ev_select.c
+++ b/src/ev_select.c
@@ -197,6 +197,15 @@ static void _do_poll(struct poller *p, int exp, int wake)
 		for (count = BITS_PER_INT, fd = fds * BITS_PER_INT; count && fd < maxfd; count--, fd++) {
 			unsigned int n = 0;
 
+			if (FD_ISSET(fd, tmp_evts[DIR_RD]))
+				n |= FD_EV_READY_R;
+
+			if (FD_ISSET(fd, tmp_evts[DIR_WR]))
+				n |= FD_EV_READY_W;
+
+			if (!n)
+				continue;
+
 #ifdef DEBUG_FD
 			_HA_ATOMIC_INC(&fdtab[fd].event_count);
 #endif
@@ -210,12 +219,6 @@ static void _do_poll(struct poller *p, int exp, int wake)
 				continue;
 			}
 
-			if (FD_ISSET(fd, tmp_evts[DIR_RD]))
-				n |= FD_EV_READY_R;
-
-			if (FD_ISSET(fd, tmp_evts[DIR_WR]))
-				n |= FD_EV_READY_W;
-
 			fd_update_events(fd, n);
 		}
 	}