Re: KVM and the OOM-Killer

[James Stevens <James.Stevens@jrcs.co.uk>]

> I'd go with 64-bit at 2GB and above. It's both faster and safer.

safer, how? (apart from no lowmem exhaust).

On a different subject, the qemu documentation says a guest VM can only 
have 2Gb of memory - does this still apply when using a 64bit host O/S ?

> The lowmem load is about 0.5% of guest memory, so 48GB means 240MB
> lowmem allocated. Thin ice.

We currently only have about 12Gb used by the VM guests, so not hitting 
that issue - the rest of HIGHMEM is host disk cache.

Our experience is that the bottle-neck on number of VM guests is disk 
i/o - with loads of memory we've pretty much eliminated reads, so that 
means disk writes.

> Since you can run a 64-bit kernel with your existing userspace, at least
> you have a simple upgrade path.

Not sure I like the idea of running a 64bit user space kernel on top of 
a 32bit host, prefer to re-install.

Can I just replace my kernel with a 64bit one, or do I have to 
re-install the host O/S ?





James