diff --git a/include/haproxy/fd.h b/include/haproxy/fd.h
index 4ea24975b..faaeaa645 100644
--- a/include/haproxy/fd.h
+++ b/include/haproxy/fd.h
@@ -48,6 +48,7 @@ extern struct polled_mask *polled_mask;
 
 extern THREAD_LOCAL int *fd_updt;  // FD updates list
 extern THREAD_LOCAL int fd_nbupdt; // number of updates in the list
+extern THREAD_LOCAL int fd_highest;// highest FD known by the current thread
 
 extern int poller_wr_pipe[MAX_THREADS];
 
@@ -466,6 +467,19 @@ static inline void fd_insert(int fd, void *owner, void (*iocb)(int fd), int tgid
 	if ((global.tune.options & GTUNE_FD_ET) && iocb == sock_conn_iocb)
 		newstate |= FD_ET_POSSIBLE;
 
+	/* We must update fd_highest to reflect the highest known FD for this
+	 * thread. It's important to note that it's not necessarily the highest
+	 * FD the thread will see, it's the highest FD that was inserted by
+	 * this thread or by the main thread. The purpose is essentially to
+	 * let all threads know the highest known FD at boot, that will be
+	 * cloned into each thread, in order to limit the work range for init
+	 * functions such as fork_poller() and fd_reregister_all(). Keeping the
+	 * value thread-local substantially limits the cost, since after a few
+	 * thousand calls the value will just stop changing.
+	 */
+	if (unlikely(fd > fd_highest))
+		fd_highest = fd;
+
 	/* This must never happen and would definitely indicate a bug, in
 	 * addition to overwriting some unexpected memory areas.
 	 */
diff --git a/src/fd.c b/src/fd.c
index 2dd265527..cf77884b1 100644
--- a/src/fd.c
+++ b/src/fd.c
@@ -112,6 +112,7 @@ volatile struct fdlist update_list[MAX_TGROUPS]; // Global update list
 
 THREAD_LOCAL int *fd_updt  = NULL;  // FD updates list
 THREAD_LOCAL int  fd_nbupdt = 0;   // number of updates in the list
+THREAD_LOCAL int  fd_highest = -1; // highest FD known by the current thread
 THREAD_LOCAL int poller_rd_pipe = -1; // Pipe to wake the thread
 int poller_wr_pipe[MAX_THREADS] __read_mostly; // Pipe to wake the threads
 
@@ -836,7 +837,7 @@ void fd_reregister_all(int tgrp, ulong mask)
 {
 	int fd;
 
-	for (fd = 0; fd < global.maxsock; fd++) {
+	for (fd = 0; fd < fd_highest; fd++) {
 		if (!fdtab[fd].owner)
 			continue;
 
@@ -1271,7 +1272,7 @@ int list_pollers(FILE *out)
 int fork_poller()
 {
 	int fd;
-	for (fd = 0; fd < global.maxsock; fd++) {
+	for (fd = 0; fd < fd_highest; fd++) {
 		if (fdtab[fd].owner) {
 			HA_ATOMIC_OR(&fdtab[fd].state, FD_CLONED);
 		}