AIX 6.1 memory tuning Post: 302887753

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Operating Systems AIX AIX 6.1 memory tuning Post 302887753 by bakunin on Monday 10th of February 2014 04:13:12 PM

02-10-2014

Registered User

Quote:

Originally Posted by dzodzo

vmstat -v shows that about 20% of memory pages are pinned (that would roughly correspond to those 13 GB for kernel). Does it mean that application doesn't use memory pinning (server is running Oracle+SAP)? svmon tells me that oracle and workprocesses use about 33 MB of pinned memory, perhaps it's the way they are designed. I'll have to check on some testing system what happens, if you continually increase memory for aplication, how it will affect OS behaviour.

hmmm....

First off: Oracle is indeed using "pinned memory", because "pinned memory" is normal memory, but not allowed to be swapped out. Oracle uses it for its "SGA" (system global area) on one hand and for shared memory on the other. If you are interested in the details of allocated shared memory i suggest you use the ipcs command to analyze which process owns which shared memory segment. I can warmly recommend the man page of ipcs, it is a phantastic read.

Second: yes, the kernel accumulates memory over time, but for a different reason: "file memory" is part of the memory accounted to the kernel too, because the kernel "owns" it, so to say. When the system starts and hasn't done anything it has no idea what to put into file cache, so it is initially empty. Over time it is filled and less important things get thrown out in favor of more important ones. The vmo parameters "lru_file_repage", "maxperm" and "minperm" steer the process and i suggest you read up on the vmo command (which sets these options) to understand the process better.

By the way, as Oracle has its own file caching mechanism built into the SGA it might be a wise idea to make the SGA bigger and diminish the AIX filecache accordingly. You might also consider changing the maxperm parameter to 97% instead of its current 90%, but this will probably not have a big effect if the shown values are typical for your machines load.

I hope this helps.

bakunin

bakunin

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LEARN ABOUT MOJAVE

ipcs

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