Question

Physical Memory usage - AIX server

Asked by: MaxAix

Experts,
We have AIX 5.3 running on a standalone box with 4 GB RAM.
From past couple of weeks the physical memory has been shooting high, 100% many times and the system is paging highly.
There is nothing unusual running apart from regular applications which have been there for long.

here is svmon -G:
# svmon -G
               size      inuse       free        pin    virtual
memory      1048576    1048277        299     243096    1166071
pg space    3481600     547806

               work       pers       clnt      lpage
pin          243096          0          0          0
in use       997529          0      50748          0

also, topas command gives the top "what processes"? memory or cpu?

Please help me figure out the memory problems urgently.


Thank you
Max.

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Asked On
2005-11-02 at 09:43:57ID21616873
Tags

aix

,

memory

,

usage

Topic

IBM AIX Unix

Participating Experts
3
Points
500
Comments
7

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Answers

 

by: cpc2004Posted on 2005-11-02 at 13:42:31ID: 15212322

svmon -Pu

 

by: gheistPosted on 2005-11-02 at 22:11:05ID: 15215028

AIX manages memory this way - it pre-pages readonly pages to swap, so it can allocate huge amounts of RAM without touching disk.
run vmtune and rise (e.g. ten times ) minfree/maxfree (and add into /etc/inittab for permanent result)
Other way is allocating and touching huge amount of RAM so everything needed pages out and system gets back stable.
Other to do is spreading swap spaces around disks using "smitty lvm"
And now dig into "smitty lvm" and fix your system for good.

 

by: gheistPosted on 2005-11-02 at 22:12:19ID: 15215029

Like
/usr/samples/kernel/vmtune -f 1200 -F1280

 

by: wayhuaPosted on 2005-11-07 at 09:16:14ID: 15240569

# svmon -G
               size           inuse            free        pin       virtual
memory   1048576    1048277        299     243096    1166071
pg space  3481600     547806
               work       pers       clnt      lpage
pin          243096          0          0          0
in use      997529          0   50748          0

Your system behaves  somewhat strangely. I doubt it has been running the same apps with the same environment and apps parameters as before.
Without further system information it is difficult to give a solid diagnosis, but your svmon -G has told some interesting story:
1. The pinned pages is 243096 -- about 1G RAM is pinned. 1G of memory out of 4G is "taken away" from most processes.
2. When lots memory is used, you expect to see high number of pers and/or clnt pages for file caching, but the pers is 0 and clnt is only 50748 pages or 202M. i.e. No JFS is using the memory. You do have JFS2  (or NFS, CDROM) files but it  is quite small.
3. Now there is 997529 pages of working segment memory.  997529/104856 = 95%. The "computational memory" accounts for 95% of the 4G total memory ... this is very unusual. I would say that the system is using too much memory for working segments.
4. The paging space has 547806 pages in use, that is another 2G of virtual memory (this number may not be exact, as some pages may exist in RAM *and* PS).

Things to check :
1. Who has pinned all those memory? Is it by design or is it a program problem?
    do "ps aux" to catch the big memory user, and then "svmon -P pid" to see all details of the memory usage.
2. The system may have a bad memory leak? Not only unfreed mallocs can cause memory leak. You can have a memory leak (sort of) because of a process stays there and never issues or causes a memory disclaim.
    run "svmon -P pid" every so often to check it out
3. Do you by any chance have the paging space allocation mode changed to early? This could cause increased use of PS.
4. As always, make sure you have installed the latest patches for your OS level. This should have been the #1 suggestion.
5. If you need further assistance, run "svmon -P pid", also run "vmstat -I 2 10" when system is paging heavily, and post the output here.
6. Also do "vmo -a"  and "ioo -a" and attach the output. Please note that "vmtune" is no longer supported on AIX 5.3.


 

by: cpc2004Posted on 2005-11-15 at 06:47:38ID: 15295669

This question help you to understand the storage utlization of an AIX process
http://www.experts-exchange.com/Operating_Systems/AIX_IBMs_UNIX_OS/Q_21431873.html

 

by: MaxAixPosted on 2005-11-16 at 08:05:27ID: 15304139

Hey Ghiest and everyone,
you gave me /usr/samples/kernel/vmtune -f 1200 -F1280       two weeks ago.
I correction here, I mentioned we are using AIX 5.3, but actually its 5.2.  Does the vmtune settings and minfree and maxfree settings change.  Right now they are at 120 and 128 respectively.

Does changing minfree/maxfree help?

Thanks,
Max.

 

by: gheistPosted on 2005-11-16 at 10:10:18ID: 15305267

When there are 120 pages free it cleans 8 pages - 16k  to reach 128 pages
You need to clean more at once to make disk transfers efficient ( at least 64k - 16pages at once )

20120131-EE-VQP-002

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