Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c	(revision 187)
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c	(working copy)
@@ -32,6 +32,7 @@
 #include <sys/vdev_impl.h>
 #include <sys/fs/zfs.h>
 #include <sys/zio.h>
+#include <sys/sched.h>
 #include <geom/geom.h>
 #include <geom/geom_int.h>
 
@@ -194,6 +195,8 @@
 	zio_t *zio;
 	struct bio *bp;
 
+	sched_prio(curthread, PRIBIO);
+
 	ctx = arg;
 	for (;;) {
 		mtx_lock(&ctx->gc_queue_mtx);
Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c	(revision 187)
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c	(working copy)
@@ -72,6 +72,7 @@
 #include <sys/zfs_rlock.h>
 #include <sys/vdev_impl.h>
 #include <sys/zvol.h>
+#include <sys/sched.h>
 #include <geom/geom.h>
 
 #include "zfs_namecheck.h"
@@ -402,6 +403,8 @@
 	zvol_state_t *zv;
 	struct bio *bp;
 
+	sched_prio(curthread, PRIBIO);
+
 	zv = arg;
 	for (;;) {
 		mtx_lock(&zv->zv_queue_mtx);
Index: sys/cddl/compat/opensolaris/sys/proc.h
===================================================================
--- sys/cddl/compat/opensolaris/sys/proc.h	(revision 187)
+++ sys/cddl/compat/opensolaris/sys/proc.h	(working copy)
@@ -35,12 +35,14 @@
 #include <sys/stdint.h>
 #include <sys/smp.h>
 #include <sys/debug.h>
+#include <sys/sched.h>
+#include <sys/priority.h>
 
 #ifdef _KERNEL
 
 #define	CPU		curcpu
-#define	minclsyspri	0
-#define	maxclsyspri	0
+#define	minclsyspri	(PRIBIO + 2)
+#define	maxclsyspri	(PRIBIO + 1)
 #define	max_ncpus	mp_ncpus
 #define	boot_max_ncpus	mp_ncpus
 
@@ -60,6 +62,7 @@
 {
 	proc_t *p;
 	int error;
+	kthread_t *t;
 
 	/*
 	 * Be sure there are no surprises.
@@ -70,7 +73,13 @@
 
 	error = kproc_create(proc, arg, &p, 0, stksize / PAGE_SIZE,
 	    "solthread %p", proc);
-	return (error == 0 ? FIRST_THREAD_IN_PROC(p) : NULL);
+	if (error == 0) {
+		t = FIRST_THREAD_IN_PROC(p);
+		sched_prio(t, pri);
+		return t;
+	} else {
+		return NULL;
+	}
 }
 
 #define	thread_exit()	kproc_exit(0)