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AIX Memory

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: aixmemory-topas.jpg 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
lru_file_repage           0      1      0      0      1      boolean           D
maxclient%                90     80     90     1      100    % memory          D
maxperm%                  90     80     90     1      100    % memory          D

minperm%                  10     20     10     1      100    % memory          D
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
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aixmemory.txt · Last modified: 2013/01/26 21:19 by sjoerd