From 2d5cee6b4ef62a1cf2548c39d899a7d2f06e9dc6 Mon Sep 17 00:00:00 2001 From: Michael Kerrisk Date: Sun, 17 Mar 2013 14:53:21 +0100 Subject: [PATCH] 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 --- man7/mq_overview.7 | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/man7/mq_overview.7 b/man7/mq_overview.7 index d8c1aca0b..5eff94b07 100644 --- a/man7/mq_overview.7 +++ b/man7/mq_overview.7 @@ -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