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Limit to used pages not allocated ones [message #16403] Tue, 04 September 2007 21:26 Go to next message
arpad is currently offline  arpad
Messages: 16
Registered: November 2006
Junior Member
Hi!

Is it possible with OpenVZ to limit the used pages (which is showed in the physpages) and not the allocated (privvmpages) ones?

What happens if I set the oomguarpages to 256M limit and set privvmpages to unlimited? I saw that the oomguarpages and physpages always shows the same value. Is it real? Or if the OOM occurs this can be different?

The root of the problem is that lot of our customers runs programs which has very big difference between the privvmpages and the physpages value. They complaining all the time about this problem.

I think the allocated but unused memory means that the memory not really allocated from the physical memory. Am I right?

Thanks for any help and sorry for my late night bad English. Razz

Arpad
Re: Limit to used pages not allocated ones [message #16404 is a reply to message #16403] Wed, 05 September 2007 03:07 Go to previous message
Vasily Tarasov is currently offline  Vasily Tarasov
Messages: 1345
Registered: January 2006
Senior Member
Hi,

you wrote:
Quote:

Is it possible with OpenVZ to limit the used pages (which is showed in the physpages) and not the allocated (privvmpages) ones?
It isn't possible now, 'cause of some peculiarities of Linux memory management. Crying or Very Sad

you wrote:
Quote:

What happens if I set the oomguarpages to 256M limit and set privvmpages to unlimited?
If you do so, OOM condition will be more probable (look at http://wiki.openvz.org/Oomguarpages#oomguarpages page). If it is OK for your customers, then, I think, you can do it. At least, look at the table http://wiki.openvz.org/UBC_configuration_examples - they do it in some examples Wink

you wrote:
Quote:

I saw that the oomguarpages and physpages always shows the same value. Is it real? Or if the OOM occurs this can be different?
physpages parameter accounts only used RAM, while oomguarpages parameter accounts RAM+SWAP. So, if you force some VE to use SWAP - this values will be different.

you wrote:
Quote:

I think the allocated but unused memory means that the memory not really allocated from the physical memory. Am I right?
Yes, you're right.

you wrote:
Quote:


The root of the problem is that lot of our customers runs programs which has very big difference between the privvmpages and the physpages value. They complaining all the time about this problem.
Yeap, this is a commons problem. I think the table http://wiki.openvz.org/UBC_configuration_examples can help you to make right desicion. Smile

HTH,
Vasily
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