Add new mmap(2) flags to permit applications to request specific virtual

address alignment of mappings.
- MAP_ALIGNED(n) requests a mapping aligned on a boundary of (1 << n).
  Requests for n >= number of bits in a pointer or less than the size of
  a page fail with EINVAL.  This matches the API provided by NetBSD.
- MAP_ALIGNED_SUPER is a special case of MAP_ALIGNED.  It can be used
  to optimize the chances of using large pages.  By default it will align
  the mapping on a large page boundary (the system is free to choose any
  large page size to align to that seems best for the mapping request).
  However, if the object being mapped is already using large pages, then
  it will align the virtual mapping to match the existing large pages in
  the object instead.
- Internally, VMFS_ALIGNED_SPACE is now renamed to VMFS_SUPER_SPACE, and
  VMFS_ALIGNED_SPACE(n) is repurposed for specifying a specific alignment.
  MAP_ALIGNED(n) maps to using VMFS_ALIGNED_SPACE(n), while
  MAP_ALIGNED_SUPER maps to VMFS_SUPER_SPACE.
- mmap() of a device object now uses VMFS_OPTIMAL_SPACE rather than
  explicitly using VMFS_SUPER_SPACE.  All device objects are forced to
  use a specific color on creation, so VMFS_OPTIMAL_SPACE is effectively
  equivalent.

Reviewed by:	alc
MFC after:	1 month

1 files changed, 6 insertions, 2 deletions

diff --git a/sys/vm/vm_map.h b/sys/vm/vm_map.h
index ed8864e..054c506 100644
--- a/sys/vm/vm_map.h
+++ b/sys/vm/vm_map.h
@@ -339,12 +339,16 @@ long vmspace_resident_count(struct vmspace *vmspace);
 #define	VM_FAULT_READ_AHEAD_MAX		min(atop(MAXPHYS) - 1, UINT8_MAX)
 
 /*
- * The following "find_space" options are supported by vm_map_find()
+ * The following "find_space" options are supported by vm_map_find().
+ *
+ * For VMFS_ALIGNED_SPACE, the desired alignment is specified to
+ * the macro argument as log base 2 of the desired alignment.
  */
 #define	VMFS_NO_SPACE		0	/* don't find; use the given range */
 #define	VMFS_ANY_SPACE		1	/* find a range with any alignment */
 #define	VMFS_OPTIMAL_SPACE	2	/* find a range with optimal alignment*/
-#define	VMFS_ALIGNED_SPACE	3	/* find a superpage-aligned range */
+#define	VMFS_SUPER_SPACE	3	/* find a superpage-aligned range */
+#define	VMFS_ALIGNED_SPACE(x)	((x) << 8) /* find a range with fixed alignment */
 
 /*
  * vm_map_wire and vm_map_unwire option flags