Re: [PATCH v2 6/8] kvm tools: Add rwlock wrapper

Sasha Levin
2011-05-30T11:58:31Z

On Mon, 2011-05-30 at 14:55 +0300, Pekka Enberg wrote:
> On Mon, May 30, 2011 at 2:49 PM, Ingo Molnar <mingo@elte.hu> wrote:
> > [*] Would be nice if tools/kvm/ had a debug option to simulate 'lots
> > of RAM' as well somehow - perhaps by not pre-initializing it and
> > somehow catching all-zeroes pages and keeping them all zeroes and
> > shared? It would obviously OOM after some time but would allow me
> > to at least boot a fair deal of userspace. The motivation is that
> > i have recently received a 1 TB RAM bugreport. 1 TB of RAM mapped
> > with 2MB mappings should still be able to boot to shell on a 32
> > GB RAM testbox of mine, and survive there for some time. We could
> > even do some kernel modifications to make this kind of simulation
> > easier.
>
> Doesn't our mmap() overcommit work for you? IIRC, Sasha booted guests
> with huge amounts of overcommitted RAM.

It should. I can (easily) boot 64GB guest on my 4GB laptop. We fail at
>64GB due to an issue with our mappings (I haven't investigated it yet)
- not due to running out of memory.

--

Sasha.