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Full Discussion: High memory usage in AIX 5.1
Operating Systems AIX High memory usage in AIX 5.1 Post 302167516 by bakunin on Thursday 14th of February 2008 04:31:14 PM
Old 02-14-2008
Quote:
Originally Posted by jayakumarrt
Thanks for the reply.One thing i am wondering.Sometime back the server was having 4GB ram and recently upgraded to 8 GB.Before upgrading from 4 to 8 GB RAM it was showing 99% memory usage & after upgradation also the same case..

Can anybody throw light on this. ?
If you have the output of "vmstat" from before the upgrade ready have a look at it: i bet you will see a lot of swapping going on and probably now you won't see any (or at least much less than before). The same is perhaps true for the output of "lsps -a", which tells you about the utilization of the swapspaces: perhaps the numbers decreased steeply after upgrading the RAM.

UNIX tries to use the RAM given to it as efficiently as possible: First all the processes started get the memory they need. Some memory is set aside for network buffers, file cache, etc. If still memory is available these buffers will increase in size - which buffers increases how much depends on how the machine is used: more disk-I/O, more network traffic, etc.. The administrator can tune the kernel built-in heuristics with the tools vmo (virtual memory options), schedo (scheduler options), no (network options) and ioo (I/O-options). See the manpages of these tools and the documentation of /etc/tunables for more information.

If no memory is available after satisfying the started processes demands paging occurs: memory pages are taken from the "computational memory" (memory occupied by programs by swapping them out to the paging space) or from the "file memory" (the file cache). When and how much is taken from what can also be tuned, see the "maxperm" and "minperm" parameters in "vmo".

Of course i cannot give you a detailed documentation of the AIX kernel here: what i wrote above are only glimpses and pretty unsorted ones. If you are interested in the details there are two IBM classes (AIX System Administration III: Performance Tuning; AIX Kernel Internals; each 5 days). There are also Redbooks (IBM Redbooks | AIX 5L Practical Performance Tools and Tuning Guide, IBM Redbooks | AIX 5L Performance Tools Handbook, IBM Redbooks | Database Performance Tuning on AIX) available, read them for further details.

I hope this helps.

bakunin
 

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CACHEINFO(5)							AFS File Reference						      CACHEINFO(5)

NAME
cacheinfo - Defines configuration parameters for the Cache Manager DESCRIPTION
The cacheinfo file defines configuration parameters for the Cache Manager, which reads the file as it initializes. The file contains a single line of ASCII text and must reside in the /etc/openafs directory. Use a text editor to create it during initial configuration of the client machine; the required format is as follows: <mount>:<cache>:<size> where <mount> Names the local disk directory at which the Cache Manager mounts the AFS namespace. It must exist before the afsd program runs. The conventional value is /afs. Using any other value prevents traversal of pathnames that begin with /afs (such as pathnames to files in foreign cells that do use the conventional name). The -mountdir argument to the afsd command overrides this value. <cache> Names the local disk directory to use as a cache. It must exist before the afsd program runs. The standard value is /usr/vice/cache, but it is acceptable to substitute a directory on a partition with more available space. Although the Cache Manager ignores this field when configuring a memory cache, a value must always appear in it. The -cachedir argument to the afsd command overrides this value. <size> Specifies the cache size as a number of 1-kilobyte blocks. Larger caches generally yield better performance, but a disk cache must not exceed 90% of the space available on the cache partition (85% for AIX systems), and a memory cache must use no more than 25% of available machine memory. The -blocks argument to the afsd command overrides this value. To reset cache size without rebooting on a machine that uses disk caching, use the fs setcachesize command. To display the current size of a disk or memory cache between reboots, use the fs getcacheparms command. EXAMPLES
The following example cacheinfo file mounts the AFS namespace at /afs, establishes a disk cache in the /usr/vice/cache directory, and defines cache size as 50,000 1-kilobyte blocks. /afs:/usr/vice/cache:50000 SEE ALSO
afsd(8), fs_getcacheparms(1), fs_setcachesize(1) COPYRIGHT
IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved. This documentation is covered by the IBM Public License Version 1.0. It was converted from HTML to POD by software written by Chas Williams and Russ Allbery, based on work by Alf Wachsmann and Elizabeth Cassell. OpenAFS 2012-03-26 CACHEINFO(5)
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