Index: sys/kern/kern_vnodedumper.c
===================================================================
--- sys/kern/kern_vnodedumper.c
+++ sys/kern/kern_vnodedumper.c
@@ -60,6 +60,37 @@
 EVENTHANDLER_DECLARE(livedumper_dump, livedump_dump_fn);
 EVENTHANDLER_DECLARE(livedumper_finish, livedump_fn);
 
+static uint8_t livedump_comp = KERNELDUMP_COMP_NONE;
+
+static int
+livedump_set_compression(SYSCTL_HANDLER_ARGS)
+{
+	int error;
+	uint8_t comp;
+
+	comp = livedump_comp;
+	error = sysctl_handle_8(oidp, &comp, 0, req);
+	if (error != 0 || req->newptr == NULL)
+		return (error);
+
+	switch (comp) {
+	case KERNELDUMP_COMP_NONE:
+	case KERNELDUMP_COMP_GZIP:
+	case KERNELDUMP_COMP_ZSTD:
+		livedump_comp = comp;
+		break;
+	default:
+		error = EINVAL;
+		break;
+	}
+
+	return (error);
+}
+SYSCTL_PROC(_kern, OID_AUTO, livedump_compression,
+    CTLTYPE_U8 | CTLFLAG_RW | CTLFLAG_CAPRW, NULL, 0,
+    livedump_set_compression, "U8",
+    "Compression to apply for kern.livedump");
+
 /*
  * Invoke a live minidump on the system.
  */
@@ -67,7 +98,8 @@
 sysctl_live_dump(SYSCTL_HANDLER_ARGS)
 {
 #if MINIDUMP_PAGE_TRACKING == 1
-	struct dumperinfo di;
+	struct diocskerneldump_arg kda;
+	struct dumperinfo di, *livedi;
 	struct vnode *vp;
 	struct file *fp;
 	void *rl_cookie;
@@ -96,6 +128,12 @@
 	di.mediaoffset = 0;
 	di.priv = vp; /* To be used by callback functions. */
 
+	bzero(&kda, sizeof(kda));
+	kda.kda_compression = livedump_comp;
+	error = dumper_create(&di, "livedump", &kda, &livedi);
+	if (error != 0)
+		return (error);
+
 	/* Lock the vnode and the entire file range. */
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 	rl_cookie = vn_rangelock_wlock(vp, 0, OFF_MAX);
@@ -108,13 +146,14 @@
 		goto out;
 
 	dump_savectx();
-	error = minidumpsys(&di, true);
+	error = minidumpsys(livedi, true);
 	/* XXX: may clobber error. */
 	EVENTHANDLER_INVOKE(livedumper_finish, &error);
 out:
 	sx_xunlock(&livedump_sx);
 	vn_rangelock_unlock(vp, rl_cookie);
 	VOP_UNLOCK(vp);
+	dumper_destroy(livedi);
 	return (error);
 #else
 	return (EOPNOTSUPP);