| mmap.2 (57550) | mmap.2 (57686) |
|---|---|
| 1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. --- 16 unchanged lines hidden (view full) --- 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)mmap.2 8.4 (Berkeley) 5/11/95 | 1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. --- 16 unchanged lines hidden (view full) --- 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)mmap.2 8.4 (Berkeley) 5/11/95 |
| 33.\" $FreeBSD: head/lib/libc/sys/mmap.2 57550 2000-02-28 04:10:35Z ps $ | 33.\" $FreeBSD: head/lib/libc/sys/mmap.2 57686 2000-03-02 09:14:21Z sheldonh $ |
| 34.\" 35.Dd May 11, 1995 36.Dt MMAP 2 37.Os BSD 4 38.Sh NAME 39.Nm mmap 40.Nd map files or devices into memory 41.Sh SYNOPSIS --- 86 unchanged lines hidden (view full) --- 128.Xr execve 2 129system calls. 130.It Dv MAP_PRIVATE 131Modifications are private. 132.It Dv MAP_SHARED 133Modifications are shared. 134.It Dv MAP_STACK 135This option is only available if your system has been compiled with | 34.\" 35.Dd May 11, 1995 36.Dt MMAP 2 37.Os BSD 4 38.Sh NAME 39.Nm mmap 40.Nd map files or devices into memory 41.Sh SYNOPSIS --- 86 unchanged lines hidden (view full) --- 128.Xr execve 2 129system calls. 130.It Dv MAP_PRIVATE 131Modifications are private. 132.It Dv MAP_SHARED 133Modifications are shared. 134.It Dv MAP_STACK 135This option is only available if your system has been compiled with |
| 136VM_STACK defined when compiling the kernel. This is the default for 137i386 only. Consider adding -DVM_STACK to COPTFLAGS in your /etc/make.conf 138to enable this option for other architechures. MAP_STACK implies | 136VM_STACK defined when compiling the kernel. 137This is the default for 138i386 only. 139Consider adding -DVM_STACK to COPTFLAGS in your /etc/make.conf 140to enable this option for other architechures. 141MAP_STACK implies |
| 139MAP_ANON, and 140.Fa offset 141of 0. 142.Fa fd 143must be -1 and 144.Fa prot 145must include at least PROT_READ and PROT_WRITE. This option creates 146a memory region that grows to at most --- 122 unchanged lines hidden (view full) --- 269.Xr munmap 2 , 270.Xr getpagesize 3 271.Sh BUGS 272.Ar len 273is limited to 2GB. Mmapping slightly more than 2GB doesn't work, but 274it is possible to map a window of size (filesize % 2GB) for file sizes 275of slightly less than 2G, 4GB, 6GB and 8GB. 276.Pp | 142MAP_ANON, and 143.Fa offset 144of 0. 145.Fa fd 146must be -1 and 147.Fa prot 148must include at least PROT_READ and PROT_WRITE. This option creates 149a memory region that grows to at most --- 122 unchanged lines hidden (view full) --- 272.Xr munmap 2 , 273.Xr getpagesize 3 274.Sh BUGS 275.Ar len 276is limited to 2GB. Mmapping slightly more than 2GB doesn't work, but 277it is possible to map a window of size (filesize % 2GB) for file sizes 278of slightly less than 2G, 4GB, 6GB and 8GB. 279.Pp |
| 277The limit is imposed for a variety of reasons. Most of them have to do | 280The limit is imposed for a variety of reasons. 281Most of them have to do |
| 278with 279.Tn FreeBSD 280not wanting to use 64 bit offsets in the VM system due to | 282with 283.Tn FreeBSD 284not wanting to use 64 bit offsets in the VM system due to |
| 281the extreme performance penalty. So | 285the extreme performance penalty. 286So |
| 282.Tn FreeBSD 283uses 32bit page indexes and 284this gives 285.Tn FreeBSD | 287.Tn FreeBSD 288uses 32bit page indexes and 289this gives 290.Tn FreeBSD |
| 286a maximum of 8TB filesizes. It's actually bugs in | 291a maximum of 8TB filesizes. 292It's actually bugs in |
| 287the filesystem code that causes the limit to be further restricted to 2881TB (loss of precision when doing blockno calculations). 289.Pp 290Another reason for the 2GB limit is that filesystem metadata can 291reside at negative offsets. 292.Pp 293We currently can only deal with page aligned file offsets. | 293the filesystem code that causes the limit to be further restricted to 2941TB (loss of precision when doing blockno calculations). 295.Pp 296Another reason for the 2GB limit is that filesystem metadata can 297reside at negative offsets. 298.Pp 299We currently can only deal with page aligned file offsets. |