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

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> From: Olaf Hering [mailto:olaf@xxxxxxxxx]

Hi Olaf --

Thanks for the reply!  Since Tim answers my questions later in the
thread, one quick comment...

> 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?

So xenpaging is fine and useful, but IMHO only in conjunction
with some other technology that reduces total physical RAM usage
to less than sum(max_mem(all VMs)).

Dan

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