topic Re: Memory Utilisation is very high in 11.31 in Operating System - HP-UX

Memory Utilisation is very high in 11.31

WW393114 — Fri, 09 Jul 2010 03:45:45 GMT

Hello,

We have installed 11.31 OS in one of the rx2660, no applications are installed in it but still memory utilisation is 64% ?? can u pls suggest how to reduce it

Re: Memory Utilisation is very high in 11.31

Michal Kapalka (mikap) — Fri, 09 Jul 2010 04:22:35 GMT

Hi,

at first how much memory do you have ???

check this docu : "HP-UX Performance Cookbook"

http://h21007.www2.hp.com/portal/download/files/unprot/devresource/Docs/TechPapers/UXPerfCookBook.pdf

mikap

Re: Memory Utilisation is very high in 11.31

WW393114 — Fri, 09 Jul 2010 06:11:55 GMT

8gb of physical memory is installed in the server. can u tell me what needs to be done to reduce this memory utilisation from 64% to 30% as no application is installed in the server

Re: Memory Utilisation is very high in 11.31

Hakki Aydin Ucar — Fri, 09 Jul 2010 06:43:25 GMT

Hi,

top OR (if you have) glance is good tool to root cause of excessive memory utility in your system.

first you have to find what process are eating memory:
# top
and use ps command to get more information about process.
# ps -ef |grep

Re: Memory Utilisation is very high in 11.31

H.Hassib — Fri, 09 Jul 2010 09:18:48 GMT

what is the swap size in this machine..

use swapinfo command to know

Re: Memory Utilisation is very high in 11.31

Pramod Kumar M — Sat, 10 Jul 2010 02:45:50 GMT

>>We have installed 11.31 OS in one of the >>rx2660, no applications are installed in >>it but still memory utilisation is 64% ?? >>can u pls suggest how to reduce it

Even if no applications are running by default OS creates some processes. As suggested in the earlier responses you need to figure using TOP and GLANCE which of those processes are consuming so much memory.

Re: Memory Utilisation is very high in 11.31

johnsonpk — Sat, 10 Jul 2010 06:08:30 GMT

lower the kernel values for the parameters,

filecache_ min and filecache_max ,

high values of filecache_max (default 50 %) may be the one tends to display to hig utilization for memory..

regards!
Johnson

Re: Memory Utilisation is very high in 11.31

WW393114 — Sun, 11 Jul 2010 02:48:25 GMT

Hi John as said i have changed those two kernel parameter's. now it got reduced to 48%. thanks to all. can i know is 48% ok or more with out any application runnung in server

Re: Memory Utilisation is very high in 11.31

johnsonpk — Sun, 11 Jul 2010 04:56:10 GMT

Hi,

From my experience anything between 3 to 5GB memory utilization for an idle system(11iV3) is normal.

Thanks!

Re: Memory Utilisation is very high in 11.31

WW393114 — Mon, 12 Jul 2010 01:50:36 GMT

ok!! Thaks to Everybody for spending your time

Re: Memory Utilisation is very high in 11.31

Steven Schweda — Mon, 12 Jul 2010 02:23:22 GMT

> [...] as said i have changed those two
> kernel parameter's.

From what, to what?

> now it got reduced to 48%. thanks to all.

Why do you care how much memory is free now,
when you're running "no applications"? I'd
expect the OS file-system cache software to
give back memory when some other process
needs it. Limiting the cache using
filecache_max may simply make your system
slower when memory is available. Is that
what you want?

What good is having unused memory?

> can i know is 48% ok or more with out any
> application runnung in server

Define "ok". My psychic powers are too weak
to tell me what your applications are, let
alone how much memory they will need. Do
_you_ know?

Re: Memory Utilisation is very high in 11.31

WW393114 — Mon, 12 Jul 2010 03:19:42 GMT

HI,

i have changed filecache_min to 7% and filechache_max to 10%.

Re: Memory Utilisation is very high in 11.31

Wim Rombauts — Mon, 12 Jul 2010 04:58:20 GMT

I have seen this high memory usage of 11.31 on my systems too. We have done a lot of research, together with HP support, to find out what all this memory was used for.

After having consulted the labs with our issue, it turned out that HP-UX 11.31 is configured to just take memory as long as there is free memory ("what good is unused memory ?") and keeps allocating new memory without any attempt to free up memory somewhere as long as there is free memory. (Why waste time on pushing data out of memory when there is still unused memory available and when there is a risk that cleaned-up data needs to be reloaded sometime later.)

Only when all free memory is used up (memory usage is nearly 100%), HP-UX will start spending time on lloking for hardly used memory regions, and clean it up, or shrink the filecache, or ...

So, I learned that high memory usage on HP-UX 11.31 is nothing to worry about.

You decreased the filecache. What for ? You have slowed down your system because it will need to go to disk more often now. But it is your choice, of course.

Re: Memory Utilisation is very high in 11.31

johnsonpk — Mon, 12 Jul 2010 05:50:57 GMT

Hi Steven/ Wim , I fully agree with your opinion , having unused memory in the system when there is a possibility of using it effectively,does not make any sense..

Not to defend your suggestions , having those tunable set to 1 GB in 30+ v3 boxes doesn't show any performance degrade , I think the below lines
justify why my systems are not impacted

on page 6 http://h20338.www2.hp.com/hpux11i/downloads/unified%20file%20cache.pdf

These were DBC_Min_PCT which specifies the minimum amount of file cache that needs to
be kept. The next tuneable was DBC_MAX_PCT and this controls the maximum amount of cache that should be
kept in the system. These two tuneables have been replaced by Filecache_min and Filecache_max. The two new
tuneables are compatible with DBC_Min_PCT, and DBC_Max_PCT tuneables. And they maintain the same
semantics. So, an application or a system administrator who has set the tuneables to a certain value in 11i
version 2 can set the same values in 11i version 3, and should get almost end performance.

The two new tuneables, just like in 11i version 2, only control the memory size or the cache size used by the
read and the write system file. If an application M-Maps the file, they are not controlled by these tuneables. The
meta-data is still maintained in the buffer cache, unlike file data, which is maintained in the page cache. Since
now the meta-data is maintained in a different cache, we have a private tuneable which specifies a percentage
of the Filecache_min and Filecache_max tuneables.
So the meta-data by default is a small percent of these two tuneable values, and that's where the meta-data is
kept. Also it's a private tuneable, so by default, our expectation is that customers don't have to change that.

"But more importantly, as I mentioned before, VXFS, which is the main file system in HP-UX, maintains its meta-data in
its own memory, controlled by its own set of tuneables."

Regards!
Johnson