Re: [PATCH RFC] hotplug-memory: refactor online_pages to separatezone growth from page onlining

[Jeremy Fitzhardinge]

Dave Hansen wrote:
> On Wed, 2008-04-02 at 14:35 -0700, Jeremy Fitzhardinge wrote:
>   
> > Dave Hansen wrote:
> >     
> > > Oh, once we've let Linux establish ptes to it, we've required that the
> > > hypervisor have it around?  How does that work with the balloon driver?
> > > Do we destroy the ptes when giving balloon memory back to the
> > > hypervisor?
> > >       
> > Yep.  It removes any mapping before handing it back to the hypervisor.
> >     
>
> Wow.  So does Xen ever use PSE to map kernel data?  That sucks.
>   

Not at present.  But I'd like to change it to manage memory in largepage 
chunks so that we can.

> Yeah, but I'm just talking about hotplugged memory.  When we add it, we
> don't have to map the added pages (since they're highmem) and don't have
> to touch their contents and zero them out, either.  Then, the balloon
> driver can notice that the memory is too large, and start to balloon it
> down.
>   

I didn't think x86-64 had a notion of highmem.

How do you prevent the pages from being used before they're ballooned out?

> > Everything also applies to x86-64.
> >     
>
> Not really, though.  We don't have the page->flags shortage or lack of
> vmemmap on x86_64.

Right now, I'd rather have a single mechanism that works for both.

   J
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/