[SOLVED] AIX using 90% of memory

elalexluna83 · 10-02-2012, 01:54 PM

Hi All, i have an AIX box running AIX 6.1 TL7 and only runs WebSphere and IHS, i noticed that the server was so slow, i contacted AIX team and they told me that this values are ok, it doesn't metter that % of memory used is above 90% whereas PageSpace is low, is that right?

Code:

           Physical   PageSpace
% Used     98.3%       0.2%
% Free      1.7%       99.8%
MB Used   4027.5MB     14.4MB
MB Free     68.5MB   8177.6MB

SecretCode · 10-02-2012, 02:27 PM

Does AIX have a "free" command like the one on Linux? Or another way of showing used memory not including buffers and cache?

There's no problem with having all your RAM used up with buffers and cache. What matters for performance is how much swapping is taking place, which would be affected by memory usage excluding buffers and cache.

What is the load average? uptime or tload will show you this - again, not sure if these exact commands are available on AIX. If load average is high, that means too many CPU tasks are queueing.

cliffordw · 10-03-2012, 03:33 AM

Hi there,

AIX generally uses all memory not needed for computational work, for filesystem cache, which means you'll typically see all memory used, and that is not a bad thing. Paging is the thing to look for most as your AIX team mentioned.

You can see how much memory is used for computational work vs filesystem cache in at least 2 ways.

If you have root access, run:

Code:

svmon -G -O unit=auto

You should see something like this:

Code:

Unit: auto
--------------------------------------------------------------------------------------
               size       inuse        free         pin     virtual  available   mmode
memory        8.00G       7.90G     106.04M       2.33G       3.49G      4.37G     Ded
pg space      8.00G     280.08M

               work        pers        clnt       other
pin           2.06G          0K         24K     273.00M
in use        3.30G       50.2M       4.55G

The "in use" line shows what is used, while the "work" column represents computational memory and the "clnt" (client pages) represents filesystem cache.

Without root access you should be able to see this on topas. To the right of the screen you will see something like this:

Code:

MEMORY
Real,MB    8192
% Comp     41
% Noncomp  56
% Client   56

PAGING SPACE
Size,MB    8192
% Used      3
% Free     97

I hope this helps.