Use MAP_NOSYNC for vnodes without any links in their filesystem.

This is necessary for vmware: it does not use an anonymous mmap for
the memory of the virtual system. In stead it creates a temp file an
unlinks it. For a 50 MB file, this results in a ot of syncing
every 30 seconds.

Reviewed by:	Matthew Dillon <dillon@backplane.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/sys/vm/vm_mmap.c b/sys/vm/vm_mmap.c
index 1721fd3..bb106f3 100644
--- a/sys/vm/vm_mmap.c
+++ b/sys/vm/vm_mmap.c
@@ -1024,6 +1024,13 @@ vm_mmap(vm_map_t map, vm_offset_t *addr, vm_size_t size, vm_prot_t prot,
 				return (error);
 			objsize = round_page(vat.va_size);
 			type = OBJT_VNODE;
+			/*
+			 * if it is a regular file without any references
+			 * we do not need to sync it.
+			 */
+			if (vp->v_type == VREG && vat.va_nlink == 0) {
+				flags |= MAP_NOSYNC;
+			}
 		}
 	}