Re: OOM

Stephen C. Tweedie (sct@redhat.com)
Fri, 23 Jul 1999 01:18:05 +0100 (BST)


Hi,

On Wed, 21 Jul 1999 10:41:00 +0200 (MEST), Bernd Paysan
<bernd.paysan@gmx.de> said:

> I like aging in principle, I just think the current aging algorithm is not
> good enough. It isn't easy to design a better one, though ;-).

That's easy to say --- but what do you think is wrong with it? The
aging algorithm is only one small part of the VM performance, remember.

> The per-process limits do nicely on single memory hogs, perhaps too
> nicely (I remember running a synthesis job on a .5 GB memory Solaris
> machine, and the synthesis process never got more than 200 MB RSS, the
> rest was swapped out. Free memory: roughly another 200 MB. Ouch).

RSS limits, properly implemented, won't do that. The surplus will be in
cache but not in the page tables, so it will be a little slower to
access than the RSS pages. It won't be totally evicted from memory
leaving unused pages lying around.

> But malicious attacks don't care about per-process limits. They can
> just fork and produce new hogs.

That's why you have per-user process limits. We already honour those.

--Stephen

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