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SubjectRe: Avoiding OOM on overcommit...?
Date
"A month of sundays ago ptb wrote:"
> "A month of sundays ago Marco Colombo wrote:"
> > On Tue, 28 Mar 2000, Peter T. Breuer wrote:
> >
> > > > Why don't you mlock() a piece of RAM (you're going to know if it's available
> > > > at mlock() time), so you never page-fault, and use it just a as cache
> > >
> > > This is a separate issue. I don't care about (heap) memory allocation. You
> > > can always ensure you have memory at startup, or die. Malloc is not an
> > > interesting or appropriate subject for the discussion. It's userlevel.
> >
> > Besides that mlock() is not "userlevel", now i understand you're focusing
> > only on stack. Having a "reserved" swap for your stack it's the same of
> > having a fixed stack. What happens if you run out of stack?
>
> No it's not the same. Firstly, if anyone runs out of stack, they're
> dead so that is not a relevant topic to bring to the table. You can't

Actually, now I come to think of it, I believe the BSD rules work:

0) the system starts with total swap+ram counting as "available
virtual ram"
1) a "secure" process must have 8MB of "available virtual ram"
before it can be started successfully (replace 8MB with rlimit, in
general).
2) every time a secure process starts up it reduces the "available
virtual ram" by 8MB.
3) a process can start up with less than 8MB available, or not reduce
the available amount by 8MB, but in that case it will be marked
"volatile", which means that it is a candidate for killing if the
kernel needs more swap/ram.
This ensures that a secure processes stack has somewhere to be paged out
to, and that therefore the kernel need never kill it when trying to
find swap space in which to put processes current stack pages.

Peter

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