Index: sys/kern/kern_ktrace.c
===================================================================
--- sys/kern/kern_ktrace.c
+++ sys/kern/kern_ktrace.c
@@ -321,13 +321,19 @@
 			req->ktr_header.ktr_type |= KTR_DROP;
 			p->p_traceflag &= ~KTRFAC_DROP;
 		}
-		mtx_unlock(&ktrace_mtx);
-		nanotime(&req->ktr_header.ktr_time);
-		req->ktr_header.ktr_type |= KTR_VERSIONED;
+		if ((p->p_traceflag & KTRFAC_VERSIONED) != 0) {
+			mtx_unlock(&ktrace_mtx);
+			nanotime(&req->ktr_header.ktr_time);
+			req->ktr_header.ktr_type |= KTR_VERSIONED;
+			req->ktr_header.ktr_version = KTR_VERSION1;
+			req->ktr_header.ktr_cpu = PCPU_GET(cpuid);
+		} else {
+			mtx_unlock(&ktrace_mtx);
+			microtime((struct timeval *)&req->ktr_header.ktr_time);
+			req->ktr_header.ktr_version = KTR_VERSION0;
+		}
 		req->ktr_header.ktr_pid = p->p_pid;
 		req->ktr_header.ktr_tid = td->td_tid;
-		req->ktr_header.ktr_cpu = PCPU_GET(cpuid);
-		req->ktr_header.ktr_version = KTR_VERSION1;
 		bcopy(td->td_name, req->ktr_header.ktr_comm,
 		    sizeof(req->ktr_header.ktr_comm));
 		req->ktr_buffer = NULL;
@@ -1214,6 +1220,8 @@
 		p->p_traceflag |= facs;
 		if (priv_check(td, PRIV_KTRACE) == 0)
 			p->p_traceflag |= KTRFAC_ROOT;
+		if (p->p_osrel > P_OSREL_KTRACE_VERSIONED)
+			p->p_traceflag |= KTRFAC_VERSIONED;
 	} else {
 		/* KTROP_CLEAR */
 		if (((p->p_traceflag &= ~facs) & KTRFAC_MASK) == 0)
@@ -1274,6 +1282,7 @@
 	struct iovec aiov[3];
 	struct mount *mp;
 	off_t lim;
+	ssize_t kthsz;
 	int datalen, buflen;
 	int error;
 
@@ -1304,6 +1313,10 @@
 	mtx_unlock(&ktrace_mtx);
 
 	kth = &req->ktr_header;
+	if (kth->ktr_version == KTR_VERSION0)
+		kthsz = sizeof(struct ktr_header_v0);
+	else
+		kthsz = sizeof(struct ktr_header);
 	KASSERT(((u_short)kth->ktr_type & ~KTR_TYPE) < nitems(data_lengths),
 	    ("data_lengths array overflow"));
 	datalen = data_lengths[(u_short)kth->ktr_type & ~KTR_TYPE];
@@ -1313,8 +1326,8 @@
 	auio.uio_segflg = UIO_SYSSPACE;
 	auio.uio_rw = UIO_WRITE;
 	aiov[0].iov_base = (caddr_t)kth;
-	aiov[0].iov_len = sizeof(struct ktr_header);
-	auio.uio_resid = sizeof(struct ktr_header);
+	aiov[0].iov_len = kthsz;
+	auio.uio_resid = kthsz;
 	auio.uio_iovcnt = 1;
 	auio.uio_td = td;
 	if (datalen != 0) {
Index: sys/sys/ktrace.h
===================================================================
--- sys/sys/ktrace.h
+++ sys/sys/ktrace.h
@@ -285,6 +285,10 @@
 #define KTRFAC_ROOT	0x80000000	/* root set this trace */
 #define KTRFAC_INHERIT	0x40000000	/* pass trace flags to children */
 #define	KTRFAC_DROP	0x20000000	/* last event was dropped */
+/*
+ * Generate versioned trace file, deorbit after stable/13 EOL
+ */
+#define	KTRFAC_VERSIONED 0x10000000
 
 #ifdef	_KERNEL
 struct ktr_io_params;
Index: sys/sys/param.h
===================================================================
--- sys/sys/param.h
+++ sys/sys/param.h
@@ -107,6 +107,7 @@
 #define	P_OSREL_CK_SUPERBLOCK		1300000
 #define	P_OSREL_CK_INODE		1300005
 #define	P_OSREL_POWERPC_NEW_AUX_ARGS	1300070
+#define	P_OSREL_KTRACE_VERSIONED	1400064
 
 #define	P_OSREL_MAJOR(x)		((x) / 100000)
 #endif