On Tue, 14 Feb 2006, Robert Brockway wrote:
On Sun, 12 Feb 2006, tiller man wrote:
The amount of memory I am allocating is almost certainly larger than the
amount of physical memory that the machine has available. Not being a linux
expert, I assumed that the machine would be able to handle this fairly
gracefully through virtual memory allocation. But it doesn't.
There has been long debate over how to handle this condition. The end result
has been a configurable solution! :)
I need to clarify this a little. The condition that vm.overcommit_memory
deals with is what happens when you try to commit more memory than is
available within the entire system (real memory & swap).
If you are just allocating more memory to the app than physical memory
then chances are you are just thrashing as others have suggested.
Thrashing has to be fairly bad to bring the system to its knees entirely.
Different 2.4 kernels dealt with this condition with varying degrees of
The difference between thrashing and overcommitting is often easy to
detect. If the harddrive light goes on and the disk appears to be very
active chances are that you are thrashing. If you overcommit the virtual
memory the system might just seem to "fade away". These are not hard and
fast rules however.
I hope that makes it a bit clearer.
Robert Brockway B.Sc. Phone: +1-905-821-2327
Senior Technical Consultant Urgent Support: +1-416-669-3073
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