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shmop.2: Explain SHMLBA in much more detail 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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Michael Kerrisk 2014-06-05 10:07:08 +02:00
parent e530d422dc
commit 2d2c6782ae
1 changed files with 9 additions and 7 deletions
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man2/shmop.2
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@ -282,14 +282,16 @@ The following system parameter affects
.\" of SHMLBA would be useful here
.B SHMLBA
Segment low boundary address multiple.
Must be page aligned.
For the current implementation, the
When explicitly specifying an attach address in a call to
.BR shmat (),
the caller should ensure that the address is a multiple of this value.
This is necessary on some architectures,
in order either to ensure good CPU cache performance or to ensure that
different attaches of the same segment have consistent views
within the CPU cache.
.B SHMLBA
value is
.BR PAGE_SIZE .
.\" FIXME That last sentence isn't true for all Linux
.\" architectures (i.e., SHMLBA != PAGE_SIZE for some architectures)
.\" -- MTK, Nov 04
is normally some multiple of the system page size
(on many Linux architectures, it is the same as the system page size).
.PP
The implementation places no intrinsic per-process limit on the
number of shared memory segments