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Document SHM_NORESERVE flag, new in 2.6.15.

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Michael Kerrisk 2006-05-02 03:00:05 +00:00
parent fd83ecfba4
commit 320479713e
1 changed files with 19 additions and 3 deletions
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22
man2/shmget.2
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@ -33,7 +33,7 @@
.\" Language and formatting clean-ups
.\" Added notes on /proc files
.\"
.TH SHMGET 2 2005-10-26 "Linux 2.6.14" "Linux Programmer's Manual"
.TH SHMGET 2 2006-05-02 "Linux 2.6.15" "Linux Programmer's Manual"
.SH NAME
shmget \- allocates a shared memory segment
.SH SYNOPSIS
@ -110,12 +110,28 @@ argument of
.BR open (2).
Presently, the execute permissions are not used by the system.
.TP
.B SHM_HUGETLB
.BR SHM_HUGETLB " (since Linux 2.6)"
Allocate the segment using "huge pages."
See the kernel source file
.I Documentation/vm/hugetlbpage.txt
for further information.
.\" FIXME 2.6.15 adds SHM_NORESERVE; document it.
.TP
.BR SHM_NORESERVE " (since Linux 2.6.15)"
This flag serves the same purpose as the
.BR mmap (2)
.B MAP_NORESERVE
flag.
Do not reserve swap space for this segment.
When swap space is reserved, one has the guarantee
that it is possible to modify the segment.
When swap space is not reserved one might get SIGSEGV upon a write
if no physical memory is available.
See also the discussion of the file
.I /proc/sys/vm/overcommit_memory
in
.Br proc (5).
.\" As at 2.6.17-rc2, this flag has no effect if SHM_HUGETLB was also
.\" specified.
.PP
When a new shared memory segment is created,
its contents are initialised to zero values, and