AIX memory usage by processes

10-23-2018

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AIX memory usage by processes

Hi, i have 2 identical web servers using AIX. I use nmon analyser to check their performance.
The server A exceeds 20% memory usage for system, 5% for cache and the rest 75% for processes. While, it uses 4% of Paging Space.
The server B exceeds 20% for system, 45% for cache and 35% for processes.

I tried using svmon, ps and topas to investigate the memory usage and finally i found at server A the processes which run at Paging Space and how much (MB) they use.

Although i cannot find which processes need that much memory 40% in server A (comparing A-75% and B-35%) and cause this issue.

Could you please help me?

If you need any output etc, just text me or pm... thank you in advance.

dim

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10-23-2018

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I regret that I am unable to hack into your servers and my crystal ball is in for servicing. Can you post some meaningful output illustrating why you think you have a problem?

It is usual for Unix/Linux servers of all flavours to keep their memory full, i.e. cached of anything they have used, just in case it can be re-used without having to wait for disk IO. Are you seeing paging space used? The output from lsps -a would show you this sort of thing. It is extreeeeemly unlikely that the two servers will have done exactly the same thing.

The output from vmstat 5 should also have a few columns about paging in & out counts.

If your server is not using paging space, then you don't generally have a memory problem. What is making you concerned?

Thanks, in advance,
Robin

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Quote:

Originally Posted by rbatte1

I regret that I am unable to hack into your servers and my crystal ball is in for servicing. Can you post some meaningful output illustrating why you think you have a problem?

It is usual for Unix/Linux servers of all flavours to keep their memory full, i.e. cached of anything they have used, just in case it can be re-used without having to wait for disk IO. Are you seeing paging space used? The output from lsps -a would show you this sort of thing. It is extreeeeemly unlikely that the two servers will have done exactly the same thing.

The output from vmstat 5 should also have a few columns about paging in & out counts.

If your server is not using paging space, then you don't generally have a memory problem. What is making you concerned?

Thanks, in advance,
Robin

Ok, first of all you have to get your crystal ball back!

Thanks for your insterest and your help in advance! as i wrote at the first post, i noted that my concerns are for that server A exceeds almost double memory for processes. If you could ask me which i should expect to use more memory is server B!

You may find below the outputs you asked..

Server A:

Code:

> lsps -a
Page Space      Physical Volume   Volume Group    Size %Used Active  Auto  Type Chksum
paging00        hdisk0            rootvg       10240MB     2   yes   yes    lv     0
hd6             hdisk0            rootvg       10240MB     2   yes   yes    lv     0

> vmstat 5
System configuration: lcpu=8 mem=4096MB ent=1,00

kthr    memory              page              faults              cpu
----- ----------- ------------------------ ------------ -----------------------
 r  b   avm   fre  re  pi  po  fr   sr  cy  in   sy  cs us sy id wa    pc    ec
 1  0 525275  5372   0   0   0   3    3   0  12 117936 242  2  2 96  0  0,06   6,4
 1  0 525275  5372   0   0   0   0    0   0  12 118346 235  2  2 96  0  0,06   6,3
 2  0 525275  5372   0   0   0   0    0   0  12 131497 243  2  2 96  0  0,07   6,8
 1  0 525275  5372   0   0   0   0    0   0  15 118115 239  2  2 96  0  0,07   6,8
 1  0 525279  5368   0   0   0   0    0   0  15 118376 245  2  2 96  0  0,06   6,3
 1  0 525279  5368   0   0   0   0    0   0  13 131583 239  2  2 96  0  0,07   6,8
 1  0 525279  5368   0   0   0   0    0   0  13 118366 242  2  2 96  0  0,06   6,5
 1  0 525280  5367   0   0   0   0    0   0  16 118352 241  2  2 96  0  0,07   6,7

Server B:

Code:

> lsps -a
Page Space      Physical Volume   Volume Group    Size %Used Active  Auto  Type Chksum
paging00        hdisk0            rootvg       10240MB     0   yes   yes    lv     0
hd6             hdisk0            rootvg       10240MB     0   yes   yes    lv     0

> vmstat 5
System configuration: lcpu=8 mem=4096MB ent=1,00

kthr    memory              page              faults              cpu
----- ----------- ------------------------ ------------ -----------------------
 r  b   avm   fre  re  pi  po  fr   sr  cy  in   sy  cs us sy id wa    pc    ec
 1  0 539268  7007   0   0   0   0    0   0  71 118825 318  2  2 96  0  0,07   7,3
 1  0 539269  7005   0   0   0   0    0   0  52 131764 290  2  2 95  0  0,08   7,6
 1  0 539269  7005   0   0   0   0    0   0  44 118343 277  2  2 96  0  0,07   7,0
 1  0 539269  7004   0   0   0   0    0   0  43 118585 280  2  2 96  0  0,07   6,9
 1  0 539269  7004   0   0   0   0    0   0  42 131689 283  2  2 95  0  0,07   7,4
 2  0 539269  7003   0   0   0   0    0   0  55 118711 304  2  2 96  0  0,07   7,3
 1  0 539269  7003   0   0   0   0    0   0  68 118550 310  2  2 96  0  0,07   7,2
 1  0 539269  7002   0   0   0   0    0   0  41 131688 269  2  2 95  0  0,07   7,2

If you need anything more as info, please guide me!

Moderator's Comments:

Please use CODE tags (as required by forum rules) whenever you post sample input, output ,or code segments.

Last edited by Don Cragun; 10-24-2018 at 12:25 PM.. Reason: Add missing CODE tags.

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10-23-2018

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Small disclaimer : i used AIX really little, most of the time migrating stuff off of it

Looks like server B in your case, has more filesystem caching activity going on.
Meaning, if this is some kind of cluster, and you failover a service which is using that filesystem, it's bound you will have slower response until same read patterns occur on serverA filesystem, and are cached to memory.

So, basically, context is required in this case.

What services are running on that server ?
How are those two servers sharing load - are requests hitting both or failover scenarios etc. ?

I mean, what doesn't actually work or works slower on specified server so you need to investigate the memory ?

Regards
Peasant.

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Thanks for your reply too..

There is no problem on functionality yet... but this is why i check the performance daily using nmon analyser, to prevent any issue! I hope so.. :P

Both servers have web services, http, java etc..
It shouldn't use that much memory for processes (server A). Actually it should work as server B.
This is why i am concerned...

I am new in AIX, but what i understood for memory usage is that the system uses some, then the processes uses whatever they need and the rest memory will be used for filesystem. In case, there is need for more memory there will be used paging space, is this correct?

If what i understood is correct, then there is problem on server A as there are processes which use paging space!

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10-25-2018

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anyone... please help!

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10-25-2018

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Quote:

Originally Posted by dim

I am new in AIX, but what i understood for memory usage is that the system uses some, then the processes uses whatever they need and the rest memory will be used for filesystem. In case, there is need for more memory there will be used paging space, is this correct?

Most systems will give up cache before they start eating into swap space, so you are not at 0% RAM.

I think what might have happened is, at some point in the past, a process on system A grew very large, large enough to start using swap, then finished or died to give it up again.

Have you tried ps aux to list processes?

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AIX memory usage by processes

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