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*CLOSED* Can OpenVZ work w/o OOM killer? [message #7495]

Mon, 16 October 2006 11:05

akie
Messages: 5
Registered: October 2006
Location: Moscow

Junior Member

Hi,

Is it possible to turn OOM killer mode off on the server with OpenVZ? Can OpenVZ work w/o it?

[Updated on: Thu, 19 October 2006 20:20] by Moderator

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Re: Can OpenVZ work w/o OOM killer? [message #7541 is a reply to message #7495]

Tue, 17 October 2006 11:24

dev
Messages: 1693
Registered: September 2005
Location: Moscow

Senior Member

what is the problem you are experiencing with OOM killer?
it is possible to turn strict overcommit imho, however, in this case memory can be used much less effecient.
Also it is possible to increase UBC oomguarpages limit, making sure, that VE is not killed if it is below the limit.

http://static.openvz.org/userbars/openvz-developer.png

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Re: Can OpenVZ work w/o OOM killer? [message #7545 is a reply to message #7541]

Tue, 17 October 2006 11:41

akie
Messages: 5
Registered: October 2006
Location: Moscow

Junior Member

I have some very imporant processes that can by no means be killed. For example, PostgreSQL. The thing is that it's improssible to predict exact upper memory limit needed for it, and, on the other hand, the situtaion when it's being killed regullary is completely abnormal. The normal situation is when OOM occurs, forked postgres processes cannot obtain memory fragments - in these cases Postgres says "out of memory" to the _new_ sessions, while _old_ sessions still work and database is alive.

Shortly, I do not want to have even miserable probability of killing of critical processes in the system.

[Updated on: Tue, 17 October 2006 11:46]

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Re: Can OpenVZ work w/o OOM killer? [message #7546 is a reply to message #7541]

Tue, 17 October 2006 11:45

akie
Messages: 5
Registered: October 2006
Location: Moscow

Junior Member

but the question is still open.

Is OOM killer a requirement for OpenVZ?

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Re: Can OpenVZ work w/o OOM killer? [message #7547 is a reply to message #7545]

Tue, 17 October 2006 11:48

dev
Messages: 1693
Registered: September 2005
Location: Moscow

Senior Member

you can simply set oomguarpages limit higher then vmprivvmpages. In this case postgres will get NULL on mmap() before OOM guarantee hit.

However, there is still one situation when OOM can happen - global memory shortage. In this case OOM selects any VE processes to kill. But this can not happen if you do not overcommit your node.

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Re: Can OpenVZ work w/o OOM killer? [message #7551 is a reply to message #7546]

Tue, 17 October 2006 12:40

dev
Messages: 1693
Registered: September 2005
Location: Moscow

Senior Member

No, it is not a _requirement_ for OpenVZ. Just a good to have thing, because in case of global shortage nothing except for OOM can help for machine to return to responding state.

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