04-26-2006
posix ipc message queue
Hello,
My question is related to "pipcs -qa" command under HP-UX 11i PA-RISC 64 bits.
We have a little C program that creates posix ipc message queues using the mq_open() system function.
The program fail with 'No space left on device' error when we create big queues. What is the system limit of the size of all queues ?
If we calculates the sum of all the MNUM*QBYTES columns in the output of 'pipcs -qa' the error arrive when we are close to 860 or 900 Mbytes.
Is there a way to go beyond this amount of memory ?
How the system actually allocate the memory when we create a posix queue of 1024 bytes for a message and for example 100000 as the max number of messages ? Are the 1024 * 100000 bytes allocated when the queue is created or at usage time that is when we really put some messages on the queue ?
Is this related to the fact that HP-UX divide his memory space into 4 quadrants of 1GB each ? Is there a workaround ?
I already compiled the program using the 64 bit options of the K&R
style "bundled" compiler, I also tried 'setmemwindow' without success...
I'm not sure if posix IPC message queues are implemented using the mmap() function, if it is, then what is the max. shared memory size of mmap() ?
I also failed to convince users not to use so big queues...
If we cannot go beyond 900 Mbytes for the size of all queues we are planning to use something else like Java JMS or MQseries or a database ...
Thanks for your advice (and for reading this long post),
Cengiz ADANIR
Last edited by cadanir; 04-27-2006 at 09:21 AM..
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IPCS(1) BSD General Commands Manual IPCS(1)
NAME
ipcs -- report System V interprocess communication facilities status
SYNOPSIS
ipcs [-abcmopqstMQST] [-C system] [-N core]
DESCRIPTION
The ipcs program provides information on System V interprocess communication (IPC) facilities on the system.
The options are as follows:
-a Show the maximum amount of information possible when displaying active semaphores, message queues, and shared memory segments. (This
is shorthand for specifying the -b, -c, -o, -p, and -t options.)
-b Show the maximum allowed sizes for active semaphores, message queues, and shared memory segments. The ``maximum allowed size'' is
the maximum number of bytes in a message on a message queue, the size of a shared memory segment, or the number of semaphores in a
set of semaphores.
-c Show the creator's name and group for active semaphores, message queues, and shared memory segments.
-m Display information about active shared memory segments.
-o Show outstanding usage for active message queues, and shared memory segments. The ``outstanding usage'' is the number of messages in
a message queue, or the number of processes attached to a shared memory segment.
-p Show the process ID information for active semaphores, message queues, and shared memory segments. The ``process ID information'' is
the last process to send a message to or receive a message from a message queue, the process that created a semaphore, or the last
process to attach or detach a shared memory segment.
-q Display information about active message queues.
-s Display information about active semaphores.
-t Show access times for active semaphores, message queues, and shared memory segments. The access times is the time of the last con-
trol operation on an IPC object, the last send or receive of a message, the last attach or detach of a shared memory segment, or the
last operation on a semaphore.
-C system
Extract the name list from the specified system instead of the default ``/netbsd''.
-M Display system information about shared memory.
-N core
Extract values associated with the name list from the specified core instead of the default ``/dev/kmem''. and semaphores.
-Q Display system information about messages queues.
-S Display system information about semaphores.
-T Display system information about shared memory, message queues and semaphores. (This is shorthand for specifying the -M, -Q, and -S
options.)
If none of the -M, -m, -Q, -q, -S, -s, or -T options are specified, information about all active IPC facilities is listed.
RESTRICTIONS
System data structures may change while ipcs is running; the output of ipcs is not guaranteed to be consistent.
FILES
/dev/kmem default kernel memory
/netbsd default system name list
SEE ALSO
ipcrm(1), shmat(2), shmctl(2), shmdt(2), shmget(2)
AUTHORS
Thorsten Lockert <tholo@sigmasoft.com>
BUGS
This manual page is woefully incomplete, because it does not at all attempt to explain the information printed by ipcs.
BSD
March 21, 2004 BSD