Re: [Xen-devel] Pointed questions re Xen memory overcommit

[Olaf Hering <olaf@xxxxxxxxx>]

On Mon, Feb 27, Dan Magenheimer wrote:

> > From: Olaf Hering [mailto:olaf@xxxxxxxxx]
> > To me memory overcommit means swapping, which is what xenpaging does:
> > turn the whole guest gfn range into some sort of virtual memory,
> > transparent to the guest.
> > 
> > xenpaging is the red emergency knob to free some host memory without
> > caring about the actual memory constraints within the paged guests.
> 
> Sure, but the whole point of increasing RAM in one or more guests
> is to increase performance, and if overcommitting *always* means
> swapping, why would anyone use it?

The usage patterns depend on the goal. As I wrote, swapping frees host
memory so it can be used for something else, like starting yet another
guest on the host.

Olaf

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