Robin Holt wrote: > On Sat, Jan 12, 2008 at 09:51:56PM +0200, Avi Kivity wrote: > >> Christoph Lameter wrote: >> >>> On Thu, 10 Jan 2008, Avi Kivity wrote: >>> >>> >>> >>>> Actually sharing memory is possible even without this patch; one simply >>>> mmap()s a file into the address space of both guests. Or are you >>>> referring to >>>> something else? >>>> >>>> >>> A file from where? If a file is read by two guests then they will have >>> distinct page structs. >>> >>> >>> >> Two kvm instances mmap() the file (from anywhere) into the guest address >> space. That memory is shared, and will be backed by the same page structs >> at the same offset. >> > > That sounds nice, but... > > For larger machine configurations, we have different memory access > capabilities. When a partition that is located close to the home node > of the memory accesses memory, it is normal access. When it is further > away, they get special access to the line. Before the shared line is > sent to the reading node, it is converted by the memory controller into > an exclusive request and the reading node is handed the only copy of > the line. If we gave a remote kernel access to the page, we would also > open the entire owning nodes page tables up to speculative references > which effectively would be viewed by hardware as cache-line contention. > > Additionally, we have needs beyond memory backed by files. Including > special devices which do not have struct pages at all (see mspec.c). >
I don't understand. I was just explaining how kvm shares memory among guests (which does not require mmu notifiers); if you have some other configuration that can benefit from mmu notifiers, then, well, great. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
