On Wed, Jan 23, 2008 at 12:27:57PM +0200, Avi Kivity wrote: >> The approach with the export notifier is page based not based on the >> mm_struct. We only need a single page count for a page that is exported to >> a number of remote instances of linux. The page count is dropped when all >> the remote instances have unmapped the page. > > That won't work for kvm. If we have a hundred virtual machines, that means > 99 no-op notifications.
But 100 callouts holding spinlocks will not work for our implementation and even if the callouts are made with spinlocks released, we would very strongly prefer a single callout which messages the range to the other side. > Also, our rmap key for finding the spte is keyed on (mm, va). I imagine > most RDMA cards are similar. For our RDMA rmap, it is based upon physical address. >> There is only the need to walk twice for pages that are marked Exported. >> And the double walk is only necessary if the exporter does not have its >> own rmap. The cross partition thing that we are doing has such an rmap and >> its a matter of walking the exporters rmap to clear out the external >> references and then we walk the local rmaps. All once. >> > > The problem is that external mmus need a reverse mapping structure to > locate their ptes. We can't expand struct page so we need to base it on mm > + va. Our rmap takes a physical address and turns it into mm+va. > Can they wait on that bit? PageLocked(page) should work, right? We already have a backoff mechanism so we expect to be able to adapt it to include a PageLocked(page) check. Thanks, Robin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
