Re: [GIT PULL] mm: frontswap (for 3.2 window)

Konrad Rzeszutek Wilk
2011-11-16T14:51:31Z

On Tue, Nov 15, 2011 at 09:33:40AM -0800, Jeremy Fitzhardinge wrote:
> On 11/15/2011 08:29 AM, Rik van Riel wrote:
> > On 11/02/2011 05:14 PM, Dan Magenheimer wrote:
> >
> >> It occurs to me that batching could be done locally without
> >> changing the in-kernel "API" (i.e. frontswap_ops)... the
> >> guest-side KVM tmem-backend-driver could do the compression
> >> into guest-side memory and make a single
> >> hypercall=vmexit/vmenter whenever it has collected enough for
> >> a batch.
> >
> > That seems like the best way to do it, indeed.
> >
> > Do the current hooks allow that mode of operation,
> > or do the hooks only return after the entire operation
> > has completed?
>
> The APIs are synchronous, but need only return once the memory has been
> dealt with in some way. If you were batching before making a hypercall,
> then the implementation would just have to make a copy into its private
> memory and you'd have to make sure that lookups on batched but
> unsubmitted pages work.
>
> (It's been a while since I've looked at these patches, but I'm assuming
> nothing fundamental has changed about them lately.)

Yup, what you describe is possible, and nothing fundamental has changed about
them.