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mq_overview.7: Update discussion of HARD_MSGMAX 

The limit has changed in 2.6.33 and then again in 3.5.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2013-03-17 14:53:21 +01:00
parent 8ef5d0c5ce
commit 2d5cee6b4e
1 changed files with 12 additions and 3 deletions
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15
man7/mq_overview.7
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@ -151,9 +151,7 @@ The default value for
is 10.
The minimum value is 1 (10 in kernels before 2.6.28).
The upper limit is
.BR HARD_MSGMAX :
.IR "(131072\ /\ sizeof(void\ *))"
(32768 on Linux/86).
.BR HARD_MSGMAX .
The
.I msg_max
limit is ignored for privileged processes
@ -161,6 +159,17 @@ limit is ignored for privileged processes
but the
.BR HARD_MSGMAX
ceiling is nevertheless imposed.
The definition of
.BR HARD_MSGMAX
has changed across kernel versions:
before Linux 2.6.33, it was
.IR "(131072\ /\ sizeof(void\ *))"
(32768 on Linux/86);
from Linux 2.6.33, it was
.IR "(32768\ *\ sizeof(void\ *)/4)" ;
since Linux 3.5,
.\" commit 5b5c4d1a1440e94994c73dddbad7be0676cd8b9a
it is 65,536.
.TP
.I /proc/sys/fs/mqueue/msgsize_max
This file can be used to view and change the ceiling on the