diff --git a/share/man/man4/xen.4 b/share/man/man4/xen.4
--- a/share/man/man4/xen.4
+++ b/share/man/man4/xen.4
@@ -73,6 +73,14 @@
 Exports local block devices or files to other Xen domains where they can
 then be imported via
 .Nm blkfront .
+Loader tunable and
+.Xr sysctl 3
+entry
+.Va hw.xbd.xbb_reserved_new_bios
+configures the number of the
+.Vt bio
+items preallocated and reserved for
+.Nm blkback .
 .It Nm blkfront
 Import block devices from other Xen domains as local block devices, to be
 used for file systems, swap, etc.
diff --git a/sys/dev/xen/blkback/blkback.c b/sys/dev/xen/blkback/blkback.c
--- a/sys/dev/xen/blkback/blkback.c
+++ b/sys/dev/xen/blkback/blkback.c
@@ -72,6 +72,7 @@
 #include <vm/vm.h>
 #include <vm/vm_extern.h>
 #include <vm/vm_kern.h>
+#include <vm/uma.h>
 
 #include <xen/xen-os.h>
 #include <xen/blkif.h>
@@ -753,8 +754,20 @@
 
 	/** Got the needed data from hotplug scripts? */
 	bool			  hotplug_done;
+
+	/** Uma(9) zone for the bio */
+	uma_zone_t		  zone;
 };
 
+/*---------------------------- Global Static Data ----------------------------*/
+SYSCTL_DECL(_hw_xbd);
+
+int __read_mostly xbb_reserved_new_bios = 65536;
+
+SYSCTL_INT(_hw_xbd, OID_AUTO, xbb_reserved_new_bios, CTLFLAG_RWTUN,
+    &xbb_reserved_new_bios, 0,
+    "Number of reserved new xen blkback bios for non-blocking allocation");
+
 /*---------------------------- Request Processing ----------------------------*/
 /**
  * Allocate an internal transaction tracking structure from the free pool.
@@ -1986,7 +1999,7 @@
 	bio_idx    = 0;
 
 	if (operation == BIO_FLUSH) {
-		bio = g_new_bio();
+		bio = g_new_bio_uz(xbb->zone);
 		if (__predict_false(bio == NULL)) {
 			DPRINTF("Unable to allocate bio for BIO_FLUSH\n");
 			error = ENOMEM;
@@ -2047,7 +2060,7 @@
 				goto fail_free_bios;
 			}
 
-			bio = bios[nbio++] = g_new_bio();
+			bio = bios[nbio++] = g_new_bio_uz(xbb->zone);
 			if (__predict_false(bio == NULL)) {
 				error = ENOMEM;
 				goto fail_free_bios;
@@ -3627,6 +3640,13 @@
 		return (error);
 	}
 
+	if (xbb_reserved_new_bios > 0) {
+		xbb->zone = g_io_new_uz("xen_blkback");
+		uma_prealloc(xbb->zone, xbb_reserved_new_bios);
+		uma_zone_reserve(xbb->zone, xbb_reserved_new_bios);
+	} else
+		xbb->zone = NULL;
+
 	return (0);
 }
 
@@ -3686,6 +3706,11 @@
 		xbb->dev_name = NULL;
 	}
 
+	if (xbb->zone != NULL) {
+		uma_zdestroy(xbb->zone);
+		xbb->zone = NULL;
+	}
+
 	mtx_destroy(&xbb->lock);
         return (0);
 }