Re: Overcomittable memory

From: Peter Svensson (petersv@psv.nu)
Date: Fri Mar 17 2000 - 06:18:36 EST


On Fri, 17 Mar 2000, James Sutherland wrote:

> Yes, you COULD have COW without overcommitting - but you still lose one of
> the major benefits of COW, namely huge savings on VM usage. If I fork()
> 100 Apache processes of 20Mb each, I need perhaps 30Mb of VM total.
> WITHOUT overcommitted COW, I end up needing 2Gb of swap space - 1.98Gb of
> which I will never use! This is certainly not an efficient use of swap
> space, IMO...

Well, that depends entierly on what you use the computer for. Another
possibility is to deny writing to the text pages of a process. _Then_ you
can safely share the pages without making promises the kernel man not be
able to honour.

Peter

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