This doesn't quite work with the SPL yet

module/zfs/arc.c

@@ -3359,8 +3359,10 @@ arc_init(void)
 	 * than the addressable space (intel in 32-bit mode), we may
 	 * need to limit the cache to 1/8 of VM size.
 	 */
+#ifndef HAVE_SPL
 	arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
-#endif
+#endif /* HAVE_SPL */
+#endif /* _KERNEL */
 
 	/* set min cache to 1/32 of all memory, or 64MB, whichever is more */
 	arc_c_min = MAX(arc_c / 4, 64<<20);