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SubjectRe: Overcommitable memory??
Den 19-Mar-00 19:55:47 skrev James Sutherland følgende om "Re: Overcommitable memory??":
> On 19 Mar 2000 2:49:12 +0100, you wrote:
>> That's all theory. Reality is that Linux always overcommits memory
>>regardless of what you set /proc/sys/vm/overcommit_memory to. Proof:

> (snip sample program which does NOT touch the allocated memory)

No, of course it doesn't. Why should it? The whole point of it was to
prove that Linux always overcommits memory. It did that. The point was not
to prove that you can trivially nuke any Linux system without even being
nasty. We know that already. I didn't see any point in causing greef (lost
work, etc.) for the other users on that box. Do you?

>> I started 14 processes which each successfully allocated 64 MB. That's
>>interval. If only overcommitment could be disabled...

> How would this help? You would just allocate the memory you have
> faster, and run out of memory sooner.

It would have helped because only 3-4 of those processed would have been
allowed to run, thereby isolating the problem to the remaining 10-11

> Anyway - your system crashes to a "big red switch" state when a
> process grabs all the VM?!?! You have a serious problem there - but it
> isn't overcommit.

The problem _is_ overcommit. The proof that overcommit is the problem is
that the kernel's OOM killer sets in.

> Which process is leaking, anyway??

None. We don't have any processes doing anything wrong. We're just so
unfortunate that we're running a kernel which doesn't have even the most
basic piece of memory management.


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