On Fri, 2011-04-15 at 11:21 -0500, Anthony Liguori wrote:
> > This patch makes the "tell host first" logic the only case. This
> > should make everybody happy, and reduce the amount of untested or
> > untestable code in the kernel.
>
> It doesn't make me happy.
Darn.
> Why would we do this in QEMU? This prevents the guest from doing
> ballooning reclaim during OOM.
What the heck is "ballooning reclaim"? Could you elaborate a bit on how
this happens? I think I'm missing some subtlety here.
I think 'tell host first' is the only sane way to do it. Look at the
'tell host second code':
release_pages_by_pfn(); // let other kernel users at the pages
tell_host(); // tell the hypervisor they're used again
At the point we've started using the pages again, we haven't *told* the
host that we're using them. I think that's potentially a problem. Is
qemu somehow cool with the guest touching pages that are supposed to be
in the balloon and unusable?
-- Dave
