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Operating Systems AIX AIX memory usage by processes Post 303025236 by dim on Monday 29th of October 2018 05:47:24 AM
Old 10-29-2018
Quote:
Originally Posted by MadeInGermany
Yes, shared memory is often not considered, because it can be used by many process - or it is counted several times.

A special type of shared memory is the SysV IPC (inter process communication), listed with
Code:
ipcs -p

E.g. for the "Shared Memory" the listed PIDs are for the "Creator" and the "Last attacher".

Even the normal fork/exec to create a new process produces shared memory.
Because initially they are identical, they are not actually copied but the new process reuses the memory. They are really copied when the new process modifies it. This is called COW (copy on write).
Your last sentence is the explanation of why two identical servers have different usage of memory? To be honest i tried to read man page of ipcs. I can give you the output of those 2 servers... but i still cannot understand it.... Smilie

I am about to give it up.. Smilie

My next shot is to reboot the server which confuses me and check its reaction... Smilie

But i would like to have any "evidence" to approve the need of reboot!
Smilie
 

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IPCS(1) 						    BSD General Commands Manual 						   IPCS(1)

NAME
ipcs -- report System V interprocess communication facilities status SYNOPSIS
ipcs [-abcMmopQqSsTt] DESCRIPTION
The ipcs utility 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 system information about shared memory. -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 system information about messages queues. -q Display information about active message queues. -S Display system information about semaphores. -s Display information about active semaphores. -T Display system information about shared memory, message queues and 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. If none of the -M, -m, -Q, -q, -S, or -s 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. BUGS
This manual page is woefully incomplete, because it does not at all attempt to explain the information printed by ipcs. SEE ALSO
ipcrm(1) AUTHORS
Thorsten Lockert <tholo@sigmasoft.com> BSD
June 18, 1994 BSD
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