HP-UX 11i December 2001 Release Notes

Process, Threads, Memory, and Kernel Parameters
System-V IPC Message Queue Enhancement
Chapter 8
151
These concerns arise only for separately-built binaries which share common message
queues. A group of binary programs which uses queues less than or equal to 64K are not
affected by a separate group of programs which may be using other queues greater than
64K.
The special compile-time symbol, __BIGMSGQUEUE_ENABLED, selects the enhanced
capabilities. It is anticipated that, at the major release to follow 11i, the default will be
switched so that programs recompiled without this symbol will create big queues.
Programs recompiled on 11i will be capable of handling the larger queue size fields, even
if not compiled with __BIGMSGQUEUE_ENABLED. You should consider whether your
applications should be recompiled on 11i to prepare for that future release.
Performance Issues
The purpose of increasing the size limits on System-V IPC message queues is to improve
performance of applications which pass large messages between processes. Specifically,
increased size limits eliminate the necessity to break messages into smaller pieces, as
well as reduce the high rate of context switching associated with such techniques.
Documentation Changes
The msgget (2), msgctl (2), and glossary (9) manpages have been modified to reflect these
changes.