Table of Contents
AIX Memory
Summary: ALthough AIX is by now on version 7.3 I find these old pages so fascinating I decided to keep them. On this page I'll show you how to work with AIX memory. This page is for AIX 5.3 and AIX 6.1.
Date: Between 2010-2013
Refactor: 21 December 2024: Checked formatting.
Introduction
This article handles AIX memory, info about it and the configuration. Please note that it is not a complete page! I just have to optimize the memory configuration on a few boxes and thought I post my research here.
Memory information
Amount of memory in the system:
# lsattr -El mem0 goodsize 640 Amount of usable physical memory in Mbytes False size 640 Total amount of physical memory in Mbytes False
# lsattr -El sys0 -a realmem realmem 655360 Amount of usable physical memory in Kbytes False
Memory Usage
You can use the command 'topas' to view current server resources:
Important:
| PAGING SPACE, % Used | Percentage paging space what is being used |
| PAGING, PageIn | Memory pages that are being transferred to the paging space |
| PAGING, Pageout | Memory pages that are being transferred from the paging space to memory |
If the percentage of used paging space gets to high, or you see too much pages being transferred to paging space and back you're experiencing swapping and should consider adding more memory or tuning your settings.
Top usage
This is the command to show the processes which utilize the most memory:
root@qmodel1:/>svmon -Pt15 | perl -e 'while(<>){print if($.==2||$&&&!$s++);$.=0 if(/^-+$/)}'
-------------------------------------------------------------------------------
Pid Command Inuse Pin Pgsp Virtual 64-bit Mthrd 16MB
368976 oracle 6726101 65584 578648 2188967 Y N N
364848 oracle 6688947 65584 575603 2186445 Y N N
385466 oracle 6687989 65584 576948 2186861 Y N N
209378 oracle 6685939 65584 575486 2185793 Y N N
217470 oracle 6587121 65584 575331 2185872 Y N N
462950 oracle 6586439 65584 575842 2185769 Y N N
159860 oracle 5895989 65584 575090 2185593 Y N N
336170 oracle 3627823 65584 575501 2185557 Y N N
549176 oracle 3577342 65584 575219 2185538 Y N N
573950 oracle 3577274 65584 575089 2185330 Y N N
246134 oracle 3577210 65584 575410 2185591 Y N N
299504 oracle 3568335 65584 575294 2185338 Y N N
356566 oracle 3452641 65584 575023 2185329 Y N N
180518 oracle 3446320 65584 575236 2185587 Y N N
307702 oracle 3446201 65584 575112 2185325 Y N N
Memory tuning
lru_file_repage maxclient, maxperm, minperm
The AIX lru_file_repage kernel tuning parameter was introduced in AIX V5.2 ML5 and AIX V5.3 ML2. The default setting for lru_file_repage is 1 (on). Before lru_file_repage was introduced, it was often necessary to alter minperm and maxperm/maxclient to get good performance, particularly when running an Oracle RDBMS workload. Now that lru_file_repage is available, when installing AIX V5.3 at ML5 and above it is best to leave minperm, maxperm, and maxclient at their default values and to set lru_file_repage=0 (off). Subsequent AIX performance monitoring and analysis may suggest changing other vmo parameters, but it is best to start with minperm, maxperm, and maxclient at their default values unless other AIX V5.3 initial tuning recommendations come from some authoritative source. (The VMM Tuning Tip: Protecting Computational Memory article cited on the Performance Monitoring Documentation web page suggests setting minperm=5, maxperm=90, and maxclient=90 when setting lru_file_repage=0.) Source
Adjusting these settings
Adjusting the settings according to the VMM Tuning tip would be done like this:
# vmo -p -o minperm%=5 -o maxperm%=90 -o maxclient%=90 -o lru_file_repage=0
| -p | Adjust the current values as well as the value it should have after a reboot (permanent) |
| -o | Specific option you want to adjust |
| -L | Displays current, default and possible settings (see below) |
Before lru_file_repage was introduced, you would have to set these numbers a bit otherwise:
# vmo -p -o minperm%=5 -o maxperm%=30 -o maxclient%=30
Viewing these settings
# vmstat -v
2097152 memory pages
2017044 lruable pages
201021 free pages
2 memory pools
260312 pinned pages
80.0 maxpin percentage
10.0 minperm percentage
90.0 maxperm percentage
74.5 numperm percentage
1503689 file pages
0.0 compressed percentage
0 compressed pages
74.5 numclient percentage
90.0 maxclient percentage
1503689 client pages
0 remote pageouts scheduled
2625 pending disk I/Os blocked with no pbuf
0 paging space I/Os blocked with no psbuf
2484 filesystem I/Os blocked with no fsbuf
0 client filesystem I/Os blocked with no fsbuf
838 external pager filesystem I/Os blocked with no fsbuf
0 Virtualized Partition Memory Page Faults
0.00 Time resolving virtualized partition memory page faults
bash-3.00# vmo -L
NAME CUR DEF BOOT MIN MAX UNIT TYPE
DEPENDENCIES
--------------------------------------------------------------------------------
<<<cut>>>
--------------------------------------------------------------------------------
lru_file_repage 0 1 0 0 1 boolean D
--------------------------------------------------------------------------------
maxclient% 90 80 90 1 100 % memory D
maxperm%
minperm%
--------------------------------------------------------------------------------
maxperm% 90 80 90 1 100 % memory D
minperm%
maxclient%
--------------------------------------------------------------------------------
minperm% 10 20 10 1 100 % memory D
maxperm%
maxclient%
<<<cut>>>
Parameter types:
S = Static: cannot be changed
D = Dynamic: can be freely changed
B = Bosboot: can only be changed using bosboot and reboot
R = Reboot: can only be changed during reboot
C = Connect: changes are only effective for future socket connections
M = Mount: changes are only effective for future mountings
I = Incremental: can only be incremented
d = deprecated: deprecated and cannot be changed
AIX 6.1
On AIX 6.1 there are some changes with these parameters:
- lru_file_repage, maxperm% and maxclient% are by default set to the correct value and are hidden. You can still see them using 'vmo -F -L'
- minperm% is set to 3 by default which is almost always correct as well