From: Olivier Houchard <ohouchard@haproxy.com>
Date: Thu, 2 Jul 2026 16:48:13 +0000 (+0200)
Subject: MEDIUM: listeners: Don't always balance connections across thread groups
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=3430556a882402d5c8aebb4ee891fe1a39eab1f8;p=thirdparty%2Fhaproxy.git

MEDIUM: listeners: Don't always balance connections across thread groups

Do not try to dispatch new connections to threads from other thread
groups if there is no file descriptor sharing across thread groups, as
they could not access that new fd.
---

diff --git a/src/listener.c b/src/listener.c
index 3da95f7d0..fb5123326 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -1270,12 +1270,20 @@ void listener_accept(struct listener *l)
 		if (l->rx.shard_info || atleast2(mask)) {
 			struct accept_queue_ring *ring;
 			struct listener *new_li;
+			struct shard_info *shi;
 			uint r1, r2, t, t1, t2;
 			ulong n0, n1;
 			const struct tgroup_info *g1, *g2;
 			ulong m1, m2;
 			ulong *thr_idx_ptr;
 
+			/*
+			 * Don't attempt to rebalance the connection to
+			 * other thread groups if we do not share the
+			 * file descriptor tables across thread groups.
+			 */
+			shi = (global.tune.options & GTUNE_NO_TG_FD_SHARING) ? NULL : l->rx.shard_info;
+
 			/* The principle is that we have two running indexes,
 			 * each visiting in turn all threads bound to this
 			 * listener's shard. The connection will be assigned to
@@ -1310,7 +1318,7 @@ void listener_accept(struct listener *l)
 			/* keep a copy for the final update. thr_idx is composite
 			 * and made of (n2<<16) + n1.
 			 */
-			thr_idx_ptr = l->rx.shard_info ? &((struct listener *)(l->rx.shard_info->ref->owner))->thr_idx : &l->thr_idx;
+			thr_idx_ptr = shi ? &((struct listener *)(shi->ref->owner))->thr_idx : &l->thr_idx;
 			while (1) {
 				int q0, q1, q2;
 
@@ -1322,13 +1330,13 @@ void listener_accept(struct listener *l)
 				r1 = ((uint)n0 / LONGBITS) & (LONGBITS - 1);
 
 				while (1) {
-					if (l->rx.shard_info) {
+					if (shi) {
 						/* multiple listeners, take the group into account */
-						if (r1 >= l->rx.shard_info->nbgroups)
+						if (r1 >= shi->nbgroups)
 							r1 = 0;
 
-						g1 = &ha_tgroup_info[l->rx.shard_info->members[r1]->bind_tgroup - 1];
-						m1 = l->rx.shard_info->members[r1]->bind_thread;
+						g1 = &ha_tgroup_info[shi->members[r1]->bind_tgroup - 1];
+						m1 = shi->members[r1]->bind_thread;
 					} else {
 						/* single listener */
 						r1 = 0;
@@ -1346,7 +1354,7 @@ void listener_accept(struct listener *l)
 							 * first thread of next group.
 							 */
 							t1 = 0;
-							if (l->rx.shard_info)
+							if (shi)
 								r1++;
 							/* loop again */
 							continue;
@@ -1366,19 +1374,19 @@ void listener_accept(struct listener *l)
 				 */
 				if ((global.tune.options & GTUNE_LISTENER_MQ_ANY) == GTUNE_LISTENER_MQ_FAIR) {
 					t = g1->base + t1;
-					if (l->rx.shard_info && t != tid)
-						new_li = l->rx.shard_info->members[r1]->owner;
+					if (shi && t != tid)
+						new_li = shi->members[r1]->owner;
 					goto updt_t1;
 				}
 
 				while (1) {
-					if (l->rx.shard_info) {
+					if (shi) {
 						/* multiple listeners, take the group into account */
-						if (r2 >= l->rx.shard_info->nbgroups)
-							r2 = l->rx.shard_info->nbgroups - 1;
+						if (r2 >= shi->nbgroups)
+							r2 = shi->nbgroups - 1;
 
-						g2 = &ha_tgroup_info[l->rx.shard_info->members[r2]->bind_tgroup - 1];
-						m2 = l->rx.shard_info->members[r2]->bind_thread;
+						g2 = &ha_tgroup_info[shi->members[r2]->bind_tgroup - 1];
+						m2 = shi->members[r2]->bind_thread;
 					} else {
 						/* single listener */
 						r2 = 0;
@@ -1400,7 +1408,7 @@ void listener_accept(struct listener *l)
 							 * last thread of previous group.
 							 */
 							t2 = global.maxthrpertgroup - 1;
-							if (l->rx.shard_info)
+							if (shi)
 								r2--;
 							/* loop again */
 							continue;
@@ -1429,9 +1437,9 @@ void listener_accept(struct listener *l)
 
 				/* add to this the currently active connections */
 				q0 += _HA_ATOMIC_LOAD(&l->thr_conn[ti->ltid]);
-				if (l->rx.shard_info) {
-					q1 += _HA_ATOMIC_LOAD(&((struct listener *)l->rx.shard_info->members[r1]->owner)->thr_conn[t1]);
-					q2 += _HA_ATOMIC_LOAD(&((struct listener *)l->rx.shard_info->members[r2]->owner)->thr_conn[t2]);
+				if (shi) {
+					q1 += _HA_ATOMIC_LOAD(&((struct listener *)shi->members[r1]->owner)->thr_conn[t1]);
+					q2 += _HA_ATOMIC_LOAD(&((struct listener *)shi->members[r2]->owner)->thr_conn[t2]);
 				} else {
 					q1 += _HA_ATOMIC_LOAD(&l->thr_conn[t1]);
 					q2 += _HA_ATOMIC_LOAD(&l->thr_conn[t2]);
@@ -1457,12 +1465,12 @@ void listener_accept(struct listener *l)
 					if (q0 <= q1)
 						t = tid;
 
-					if (l->rx.shard_info && t != tid)
-						new_li = l->rx.shard_info->members[r1]->owner;
+					if (shi && t != tid)
+						new_li = shi->members[r1]->owner;
 
 					t2--;
 					if (t2 >= global.maxthrpertgroup) {
-						if (l->rx.shard_info)
+						if (shi)
 							r2--;
 						t2 = global.maxthrpertgroup - 1;
 					}
@@ -1472,8 +1480,8 @@ void listener_accept(struct listener *l)
 					if (q0 <= q2)
 						t = tid;
 
-					if (l->rx.shard_info && t != tid)
-						new_li = l->rx.shard_info->members[r2]->owner;
+					if (shi && t != tid)
+						new_li = shi->members[r2]->owner;
 					goto updt_t1;
 				}
 				else { // q1 == q2
@@ -1481,12 +1489,12 @@ void listener_accept(struct listener *l)
 					if (q0 < q1) // local must be strictly better than both
 						t = tid;
 
-					if (l->rx.shard_info && t != tid)
-						new_li = l->rx.shard_info->members[r1]->owner;
+					if (shi && t != tid)
+						new_li = shi->members[r1]->owner;
 				updt_t1:
 					t1++;
 					if (t1 >= global.maxthrpertgroup) {
-						if (l->rx.shard_info)
+						if (shi)
 							r1++;
 						t1 = 0;
 					}