RS6000 AIX : Virtual memory always used up.. is this normal?

Posted on 2002-07-08
Last Modified: 2007-12-19

hi guys,

would like to ask if the virtual memory of Rs/6000 AIX is always used up as shown by "monitor -top".

Real memory:  603.5M procs  416.1M files  260.5M free 1280.0M total
Virtual memory:             409.6M used     0.0M free  409.6M total

Notice that it says 0.0M free... is this normal?
How do I track which programs is using the virtual memory and how do I ensure that everything (memory-wise) is ok..?

Please advice.
Question by:Haho
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LVL 14

Accepted Solution

chris_calabrese earned 75 total points
ID: 7138472
Most modern Unixen have a unified VM and disk cache, so all VM will be consumed for disk cache if it's not doing anything else.  This greatly improves performance, but makes it a lot harder to monitor memory usage since many tools can't tell the difference (as you've discovered).

I'm not enough of an AIX expert to help you too much here, though a simple ps -ef can usually tell you a lot about VM usage of different processes.

Expert Comment

ID: 7139004
Hi Haho

  In AIX you can use vmstat command.


Reports virtual memory statistics.


vmstat [ -f ] [ -i ] [ -s ] [ PhysicalVolume ... ] [ Interval
[ Count ] ]


The vmstat command reports statistics about kernel threads, virtual
memory, disks, traps and CPU activity. Reports generated by the vmstat
command can be used to balance system load activity. These system-wide
statistics (among all processors) are calculated as averages for values
expressed as percentages, and as sums otherwise..

    See man vmstat
LVL 14

Expert Comment

ID: 7140588
Yes, but it doesn't tell you which process is using the memory (though it can tell you the balance between disk cache activity and other demand paging).

Expert Comment

ID: 7140671

 You could try using "topas" for AIX. This is the similar to "top" and comes in the extended utilities cdrom.
   See topas output below:

  Topas Monitor for host:    YOURHOST          EVENTS/QUEUES    FILE/TTY
Tue Jul  9 11:37:19 2002   Interval:  2         Cswitch      68  Readch    57328
                                                Syscall     711  Writech    1943
Kernel    1.8   |#                           |  Reads        87  Rawin         0
User      0.6   |                            |  Writes        8  Ttyout      142
Wait      0.0   |                            |  Forks         5  Igets         0
Idle     97.5   |########################### |  Execs         5  Namei        85
                                                Runqueue    0.0  Dirblk        0
Interf   KBPS   I-Pack  O-Pack   KB-In  KB-Out  Waitqueue   1.0
en1        0.1     0.4     0.4     0.0     0.1
et1        0.0     0.0     0.0     0.0     0.0  PAGING           MEMORY
                                                Faults      635  Real,MB    2047
Disk    Busy%     KBPS     TPS KB-Read KB-Writ  Steals        0  % Comp      9.1
hdisk0    0.0      0.0     0.0     0.0     0.0  PgspIn        0  % Noncomp   4.3
hdisk1    0.0      0.0     0.0     0.0     0.0  PgspOut       0  % Client    0.5
hdisk3    0.0      0.0     0.0     0.0     0.0  PageIn        0
hdisk2    0.0      0.0     0.0     0.0     0.0  PageOut       0  PAGING SPACE
                                                Sios          0  Size,MB    1024
sleep    (32650)  1.0% PgSp: 0.1mb root                          % Used      0.6
sleep    (34028)  1.0% PgSp: 0.1mb root                          % Free     99.3
sh       (29676)  1.0% PgSp: 0.3mb root
topas    (30178)  0.5% PgSp: 0.5mb root
sh       (29934)  0.5% PgSp: 0.3mb root            Press "h" for help screen.
init     (1)      0.5% PgSp: 0.6mb root            Press "q" to quit program.
sh       (28902)  0.0% PgSp: 0.3mb root
i4lmd    (25554)  0.0% PgSp: 0.9mb root
sleep    (33028)  0.0% PgSp: 0.1mb root

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