diff options
Diffstat (limited to 'lib/libc')
| -rw-r--r-- | lib/libc/sys/mmap.2 | 53 |
1 files changed, 50 insertions, 3 deletions
diff --git a/lib/libc/sys/mmap.2 b/lib/libc/sys/mmap.2 index 73ffb2e..130f70b 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 March 18, 2012 +.Dd August 16, 2013 .Dt MMAP 2 .Os .Sh NAME @@ -97,7 +97,30 @@ Sharing, mapping type and options are specified in the argument by .Em or Ns 'ing the following values: -.Bl -tag -width MAP_HASSEMAPHORE +.Bl -tag -width MAP_PREFAULT_READ +.It Dv MAP_ALIGNED Ns Pq Fa n +Align the region on a requested boundary. +If a suitable region cannot be found, +.Fn mmap +will fail. +The +.Fa n +argument specifies the binary logarithm of the desired alignment. +.It Dv MAP_ALIGNED_SUPER +Align the region to maximize the potential use of large +.Pq Dq super +pages. +If a suitable region cannot be found, +.Fn mmap +will fail. +The system will choose a suitable page size based on the size of +mapping. +The page size used as well as the alignment of the region may both be +affected by properties of the file being mapped. +In particular, +the physical address of existing pages of a file may require a specific +alignment. +The region is not guaranteed to be aligned on any specific boundary. .It Dv MAP_ANON Map anonymous memory not associated with any specific file. The file descriptor used for creating @@ -274,6 +297,25 @@ Although this implementation does not impose any alignment restrictions on the .Fa offset argument, a portable program must only use page-aligned values. +.Pp +Large page mappings require that the pages backing an object be +aligned in matching blocks in both the virtual address space and RAM. +The system will automatically attempt to use large page mappings when +mapping an object that is already backed by large pages in RAM by +aligning the mapping request in the virtual address space to match the +alignment of the large physical pages. +The system may also use large page mappings when mapping portions of an +object that are not yet backed by pages in RAM. +The +.Dv MAP_ALIGNED_SUPER +flag is an optimization that will align the mapping request to the +size of a large page similar to +.Dv MAP_ALIGNED , +except that the system will override this alignment if an object already +uses large pages so that the mapping will be consistent with the existing +large pages. +This flag is mostly useful for maximizing the use of large pages on the +first mapping of objects that do not yet have pages present in RAM. .Sh RETURN VALUES Upon successful completion, .Fn mmap @@ -325,6 +367,10 @@ The argument was equal to zero. .It Bq Er EINVAL +.Dv MAP_ALIGNED +was specified and the desired alignment was either larger than the +virtual address size of the machine or smaller than a page. +.It Bq Er EINVAL .Dv MAP_ANON was specified and the .Fa fd @@ -356,7 +402,8 @@ was specified and insufficient memory was available. .Xr msync 2 , .Xr munlock 2 , .Xr munmap 2 , -.Xr getpagesize 3 +.Xr getpagesize 3 , +.Xr getpagesizes 3 .Sh BUGS The .Fa len |
