HP-UX 11.11 QUESTION: 2G RAM installed; only 312MB real memory available

[Eric Sun]

CPU: PA 8600-8600 CPU 3.0
Model: 9000/785/J5600
Physical Memory: 2049.8 MB
Real Memory:
Active: 278716.9 KB
Total: 324633.4 KB

When I checked the memory resource in SAM, I saw 2G physical memory installed, but only 312M real memory available. Why?

How can I make more real memory available?

Thanks.

[Jeff Schussele]

Hi Eric,

Check the kernel parms

dbc_max_pct
dbc_min_pct

If you left the default for the max - it's 50% & that can chew up a full Gig. Use bufpages & nbuf to hard set the buffer cache to around 400MB & that should free up some memory.

HTH,
Jeff

[A. Clay Stephenson]

It appears that you only printed the top portion of the display. In this case, 'Real Memory' refers to memory associated with either currently executing (Active) or executing and sleeping (Total) processes. As you spawn more processes you will see these values go up until the system cannot spawn any more processes because of kernel limits (e.g. nproc) or because no additional virtual memory is available. This is a case of 'Real' memory not being what you think it is.

[Nick W]

Eric,

Is this by any chance a new system build...?

I had seen a similar case recently when a "standard server build" was applied to a technical workstation (ie kernel tunables were set way too high and the kernel itself appeared to be 'chewing up' far too much memory resource) - reducing the kernel tunables to 'sensible' values for this particular system appeared to resolve the issue...

HTH
Nick

[Anh-Thu Tran]

We has the same problem that the total value of real memory is so far smaller than the physical memory installed. Based on the reply from Nick, which kernel tunables that we need to check to reduce and what is the sensible values that you can suggest?

[Geoff Wild]

Yes, check the dbc_max_pct and other kernel parameters...

That said, what runs on this server?

Is that with just the OS running?

Download and compile the attached c program (with the native compiler on HP).

It is called memdetail - and gives some nice info...

Another good utility - kmeminfo

Check out this thread:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=725841

Rgds...Geoff