ADSM-L

Re: Memory Tuning For AIX

2002-01-02 19:57:16
Subject: Re: Memory Tuning For AIX
From: "Anderson F. Nobre" <anderson AT SOLVO.COM DOT BR>
Date: Mon, 31 Dec 2001 18:33:14 -0200
Hi Denis,

It's too early to determine if you need a memory upgrade. First let's
analyze the situation...
At first look your CPU seems to be overcommited because the idle column is
about 11%. But if you sum the columns user and system it's about 23%. This
is your real CPU utilization, so it's too low. You can utilize until 70-80%
of your CPU.
Your wait column it's really worry! It means that you have an I/O
bottleneck. How's your iostat?
Althought the scaned pages column to be too high the relationship with
freeing is not more than 4:1, even in your case that are much pi/po. In
other words your real memory it's not overcommited.
The avm column shows that you are only using about 532MB of your real
memory. Much probably you are using most part of the other 500MB of real
memory to cache the filesystems.
If the DB, LOG e stgpool volumes are on filesystems and you are using the
defaults of VMM, so you can change these parameters through the vmtune. The
parameters that change the cache of filesystems are maxperm (-P) and minperm
(-p) to 10 and 5% respectively. The vmtune it's located on
/usr/samples/kernel.
If you don't find this directory so you need to install the
bos.adt.samples.kernel. I think that's the name of fileset. Anyway tell me
if you have some problem.
Two things you should know about vmtune: the first is that you can change
online but to feel the diference it's better to reboot the system to flush
the filesystem cache. The second is every time that you reboot your
operating system you must re-execute the vmtune with your parameters. So put
an entry in your inittab to execute the vmtune command every IPL.

Regards,

Anderson


> Hello-
> I am having a memory problem.
> I am runnning AIX 4.3.2 on a H50.  TSM is the only application
> running on the server.  When I run vmstat I get the following...
>
> kthr     memory             page              faults        cpu
> ----- ----------- ------------------------ ------------ -----------
>  r  b   avm   fre  re  pi  po  fr   sr  cy  in   sy  cs us sy id wa
>  0  0 136233   202   0   3   2  99  210   0  52  240  66 17 30 16 37
>  1  3 136234   342   0  38  11 3727 4204   0 1322 6136 4665 12 11  3 74
>  2  3 136236   160   0  44  12 3728 5326   0 1324 5844 4644 10 11  2 76
>  1  3 136237   295   0  17  19 4113 5725   0 1305 7174 5091 13 10  3 74
>  0  3 136237   629   0  19   9 4240 7442   0 1316 7200 5082 14 13  5 68
>
> Does this look normal to anyone?  From my limited understanding of vmstat
> it looks like:
> CPU utilization is maxed out
> I have blocked processes (the b column)
> The scan rate (sr) column is very high.
> The server has 1Gig of memory.  I'm really not sure how to tell how much
is
> allocated to
> the OS and how much is allocated to TSM.  Does anyone have any ideas or
> pointers is
> tuning memory for AIX?  Do I need a memory upgrade?
> I started checking this because my server response is horrible.
> Thanks.
> Denis
>
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