Index: sys/netinet/in_kdtrace.h
===================================================================
--- sys/netinet/in_kdtrace.h
+++ sys/netinet/in_kdtrace.h
@@ -65,6 +65,7 @@
 SDT_PROBE_DECLARE(tcp, , , debug__output);
 SDT_PROBE_DECLARE(tcp, , , debug__user);
 SDT_PROBE_DECLARE(tcp, , , debug__drop);
+SDT_PROBE_DECLARE(tcp, , , receive__autoresize);
 
 SDT_PROBE_DECLARE(udp, , , receive);
 SDT_PROBE_DECLARE(udp, , , send);
Index: sys/netinet/in_kdtrace.c
===================================================================
--- sys/netinet/in_kdtrace.c
+++ sys/netinet/in_kdtrace.c
@@ -132,6 +132,14 @@
     "void *", "void *",
     "int", "tcplsinfo_t *");
 
+SDT_PROBE_DEFINE6_XLATE(tcp, , , receive__autoresize,
+    "void *", "void *",
+    "struct tcpcb *", "csinfo_t *",
+    "struct mbuf *", "ipinfo_t *",
+    "struct tcpcb *", "tcpsinfo_t *" ,
+    "struct tcphdr *", "tcpinfoh_t *",
+    "int", "int");
+
 SDT_PROBE_DEFINE5_XLATE(udp, , , receive,
     "void *", "pktinfo_t *",
     "struct inpcb *", "csinfo_t *",
Index: sys/netinet/tcp_input.c
===================================================================
--- sys/netinet/tcp_input.c
+++ sys/netinet/tcp_input.c
@@ -1885,25 +1885,27 @@
 		 * the buffer to better manage the socket buffer resources.
 		 */
 			if (V_tcp_do_autorcvbuf &&
-			    (to.to_flags & TOF_TS) &&
-			    to.to_tsecr &&
-			    (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
-				if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) &&
-				    to.to_tsecr - tp->rfbuf_ts < hz) {
-					if (tp->rfbuf_cnt >
-					    (so->so_rcv.sb_hiwat / 8 * 7) &&
-					    so->so_rcv.sb_hiwat <
-					    V_tcp_autorcvbuf_max) {
-						newsize =
-						    min(so->so_rcv.sb_hiwat +
-						    V_tcp_autorcvbuf_inc,
-						    V_tcp_autorcvbuf_max);
-					}
-					/* Start over with next RTT. */
-					tp->rfbuf_ts = 0;
-					tp->rfbuf_cnt = 0;
-				} else
-					tp->rfbuf_cnt += tlen;	/* add up */
+			    (so->so_rcv.sb_flags & SB_AUTOSIZE) &&
+			    tp->t_srtt != 0 && tp->rfbuf_ts != 0 &&
+			    tcp_ts_getticks() - tp->rfbuf_ts >
+			    (tp->t_srtt >> TCP_RTT_SHIFT)) {
+				if (tp->rfbuf_cnt >
+				    (so->so_rcv.sb_hiwat / 8 * 7) &&
+				    so->so_rcv.sb_hiwat <
+				    V_tcp_autorcvbuf_max) {
+					newsize = min(
+					    so->so_rcv.sb_hiwat +
+					    V_tcp_autorcvbuf_inc,
+					    V_tcp_autorcvbuf_max);
+				}
+				TCP_PROBE6(receive__autoresize, NULL,
+				    tp, m, tp, th, newsize);
+
+				/* Start over with next RTT. */
+				tp->rfbuf_ts = 0;
+				tp->rfbuf_cnt = 0;
+			} else {
+				tp->rfbuf_cnt += tlen;	/* add up */
 			}
 
 			/* Add data to socket buffer. */
@@ -1945,10 +1947,6 @@
 		win = 0;
 	tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
 
-	/* Reset receive buffer auto scaling when not in bulk receive mode. */
-	tp->rfbuf_ts = 0;
-	tp->rfbuf_cnt = 0;
-
 	switch (tp->t_state) {
 
 	/*
Index: sys/netinet/tcp_output.c
===================================================================
--- sys/netinet/tcp_output.c
+++ sys/netinet/tcp_output.c
@@ -831,11 +831,13 @@
 			to.to_tsval = tcp_ts_getticks() + tp->ts_offset;
 			to.to_tsecr = tp->ts_recent;
 			to.to_flags |= TOF_TS;
-			/* Set receive buffer autosizing timestamp. */
-			if (tp->rfbuf_ts == 0 &&
-			    (so->so_rcv.sb_flags & SB_AUTOSIZE))
-				tp->rfbuf_ts = tcp_ts_getticks();
 		}
+
+		/* Set receive buffer autosizing timestamp. */
+		if (tp->rfbuf_ts == 0 &&
+		    (so->so_rcv.sb_flags & SB_AUTOSIZE))
+			tp->rfbuf_ts = tcp_ts_getticks();
+
 		/* Selective ACK's. */
 		if (tp->t_flags & TF_SACK_PERMIT) {
 			if (flags & TH_SYN)
Index: sys/netinet/tcp_stacks/fastpath.c
===================================================================
--- sys/netinet/tcp_stacks/fastpath.c
+++ sys/netinet/tcp_stacks/fastpath.c
@@ -435,25 +435,27 @@
 	 * the buffer to better manage the socket buffer resources.
 	 */
 	if (V_tcp_do_autorcvbuf &&
-	    (to->to_flags & TOF_TS) &&
-	    to->to_tsecr &&
-	    (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
-		if (TSTMP_GT(to->to_tsecr, tp->rfbuf_ts) &&
-		    to->to_tsecr - tp->rfbuf_ts < hz) {
-			if (tp->rfbuf_cnt >
-			    (so->so_rcv.sb_hiwat / 8 * 7) &&
-			    so->so_rcv.sb_hiwat <
-			    V_tcp_autorcvbuf_max) {
-				newsize =
-					min(so->so_rcv.sb_hiwat +
-					    V_tcp_autorcvbuf_inc,
-					    V_tcp_autorcvbuf_max);
-			}
-			/* Start over with next RTT. */
-			tp->rfbuf_ts = 0;
-			tp->rfbuf_cnt = 0;
-		} else
-			tp->rfbuf_cnt += tlen;	/* add up */
+	    (so->so_rcv.sb_flags & SB_AUTOSIZE) &&
+	    tp->t_srtt != 0 && tp->rfbuf_ts != 0 &&
+	    tcp_ts_getticks() - tp->rfbuf_ts >
+	    (tp->t_srtt >> TCP_RTT_SHIFT)) {
+		if (tp->rfbuf_cnt >
+		    (so->so_rcv.sb_hiwat / 8 * 7) &&
+		    so->so_rcv.sb_hiwat <
+		    V_tcp_autorcvbuf_max) {
+			newsize = min(
+			    so->so_rcv.sb_hiwat +
+			    V_tcp_autorcvbuf_inc,
+			    V_tcp_autorcvbuf_max);
+		}
+		TCP_PROBE6(receive__autoresize, NULL,
+		    tp, m, tp, th, newsize);
+
+		/* Start over with next RTT. */
+		tp->rfbuf_ts = 0;
+		tp->rfbuf_cnt = 0;
+	} else {
+		tp->rfbuf_cnt += tlen;  /* add up */
 	}
 
 	/* Add data to socket buffer. */
@@ -532,10 +534,6 @@
 		win = 0;
 	tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
 
-	/* Reset receive buffer auto scaling when not in bulk receive mode. */
-	tp->rfbuf_ts = 0;
-	tp->rfbuf_cnt = 0;
-
 	switch (tp->t_state) {
 
 	/*