diff --git a/sys/cam/ctl/ctl.c b/sys/cam/ctl/ctl.c
--- a/sys/cam/ctl/ctl.c
+++ b/sys/cam/ctl/ctl.c
@@ -68,6 +68,7 @@
 #include <sys/sysctl.h>
 #include <sys/nv.h>
 #include <sys/dnv.h>
+#include <machine/atomic.h>
 #include <vm/uma.h>
 
 #include <cam/cam.h>
@@ -12819,6 +12820,16 @@
 	}
 }
 
+#ifdef __i386__
+_Static_assert(sizeof(time_t) == 4, "time_t has unexpected size on this arch");
+#define atomic_add_time_t atomic_add_32
+#define atomic_load_time_t atomic_load_32
+#else
+_Static_assert(sizeof(time_t) == 8, "time_t has unexpected size on this arch");
+#define atomic_add_time_t atomic_add_64
+#define atomic_load_time_t atomic_load_64
+#endif
+
 static void
 ctl_process_done(union ctl_io *io)
 {
@@ -12832,20 +12843,40 @@
 	fe_done = port->fe_done;
 
 #ifdef CTL_TIME_IO
-	if ((time_uptime - io->io_hdr.start_time) > ctl_time_io_secs) {
-		char str[256];
-		char path_str[64];
-		struct sbuf sb;
-
-		ctl_scsi_path_string(io, path_str, sizeof(path_str));
-		sbuf_new(&sb, str, sizeof(str), SBUF_FIXEDLEN);
-
-		ctl_io_sbuf(io, &sb);
-		sbuf_cat(&sb, path_str);
-		sbuf_printf(&sb, "ctl_process_done: %jd seconds\n",
-			    (intmax_t)time_uptime - io->io_hdr.start_time);
-		sbuf_finish(&sb);
-		printf("%s", sbuf_data(&sb));
+	static volatile time_t last_warn_time = 0;
+	time_t now, io_time, llwt;
+	static volatile int suppressed_warnings = 0;
+	int lsw;
+
+	now = time_uptime;
+	io_time = now - io->io_hdr.start_time;
+	if (io_time > ctl_time_io_secs) {
+		llwt = atomic_load_time_t(&last_warn_time);
+		if (now - llwt > 1) {
+			char str[256];
+			char path_str[64];
+			struct sbuf sb;
+
+			ctl_scsi_path_string(io, path_str, sizeof(path_str));
+			sbuf_new(&sb, str, sizeof(str), SBUF_FIXEDLEN);
+
+			ctl_io_sbuf(io, &sb);
+			sbuf_cat(&sb, path_str);
+			sbuf_printf(&sb, "ctl_process_done: %jd seconds",
+			    (intmax_t)io_time);
+			lsw = atomic_swap_int(&suppressed_warnings, 0);
+			if (lsw > 0) {
+				sbuf_printf(&sb,
+					" (suppressed %d similar warnings)",
+					lsw);
+			}
+			sbuf_putc(&sb, '\n');
+			sbuf_finish(&sb);
+			printf("%s", sbuf_data(&sb));
+			atomic_add_time_t(&last_warn_time, now - llwt);
+		} else {
+			atomic_add_int(&suppressed_warnings, 1);
+		}
 	}
 #endif /* CTL_TIME_IO */