Add the MAP_PREFAULT_READ option to mmap(2).

Reviewed by:	jhb, kib

1 files changed, 14 insertions, 1 deletions

diff --git a/lib/libc/sys/mmap.2 b/lib/libc/sys/mmap.2
index b633cb1..0b1f35f 100644
--- a/lib/libc/sys/mmap.2
+++ b/lib/libc/sys/mmap.2
@@ -28,7 +28,7 @@
 .\"	@(#)mmap.2	8.4 (Berkeley) 5/11/95
 .\" $FreeBSD$
 .\"
-.Dd November 6, 2009
+.Dd August 28, 2010
 .Dt MMAP 2
 .Os
 .Sh NAME
@@ -211,6 +211,19 @@ implements a coherent file system buffer cache.
 However, it may be
 used to associate dirty VM pages with file system buffers and thus cause
 them to be flushed to physical media sooner rather than later.
+.It Dv MAP_PREFAULT_READ
+Immediately update the calling process's lowest-level virtual address
+translation structures, such as its page table, so that every memory
+resident page within the region is mapped for read access.
+Ordinarily these structures are updated lazily.
+The effect of this option is to eliminate any soft faults that would
+otherwise occur on the initial read accesses to the region.
+Although this option does not preclude
+.Fa prot
+from including
+.Dv PROT_WRITE ,
+it does not eliminate soft faults on the initial write accesses to the
+region.
 .It Dv MAP_PRIVATE
 Modifications are private.
 .It Dv MAP_SHARED