Christoph Lameter wrote: > Ahhh. Good to hear. But we will still end in a situation where only > the remote ptes point to the page. Maybe the remote instance will dirty > the page at that point? > >
When the spte is dropped, its dirty bit is transferred to the page. > >> sharing code, and for you missing a single notifier means memory >> corruption because you don't bump the page count to represent the >> external reference). >> > > 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. Also, our rmap key for finding the spte is keyed on (mm, va). I imagine most RDMA cards are similar. > > >>> @@ -966,6 +973,9 @@ int try_to_unmap(struct page *page, int >>> >>> BUG_ON(!PageLocked(page)); >>> >>> + if (unlikely(PageExported(page))) >>> + export_notifier(invalidate_page, page); >>> + >>> >> Passing the page here will complicate things especially for shared >> pages across different VM that are already working in KVM. For non >> > > How? > > >> shared pages we could cache the userland mapping address in >> page->private but it's a kludge only working for non-shared >> pages. Walking twice the anon_vma lists when only a single walk is >> > > 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. > >> Besides the pinned pages ram leak by having the zero locking window >> above I'm curious how you are going to take care of the finegrined >> aging that I'm doing with the accessed bit set by hardware in the spte >> > > I think I explained that above. Remote users effectively are forbidden to > establish new references to the page by the clearing of the exported bit. > > Can they wait on that bit? -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
