Re: Avoiding OOM on overcommit...?

From: David Whysong (dwhysong@physics.ucsb.edu)
Date: Sun Mar 26 2000 - 19:48:30 EST


On Sun, 26 Mar 2000, Richard Gooch wrote:
>Linda Walsh writes:
>> David Whysong wrote:
>> > If you run out of a resource, the system should not crash. The kernel just
>> > has to free up the resource. A convenient way of doing that is to kill a
>> > user process.
>>
>> Then you have violated the integrity of the user-process
>> space. Tell me, which processes are killed when the system runs out
>> file descriptors? How about processes? Disk space? Why are you
>> treating memory differently?
>
>Because it's different (read harder)? I still haven't seen a
>description of how we handle stack exhaustion properly. All we can do
>there is kill the offending process.

That's true, but there are other good reasons. Here are two: memory can be
implicitly allocated, and the kernel uses memory dynamically.

And actually it isn't all _that_ different. The kernel has to deny a
resource to user-space if that resource is used up. Most programs will
cease to function if you deny them a resource that they really need.
Memory is the most fundamental of resources.

Dave

David Whysong dwhysong@physics.ucsb.edu
Astrophysics graduate student University of California, Santa Barbara
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