On Wed, Feb 22, 2023 at 3:27 PM Gupta, Pankaj <pankaj.gupta@xxxxxxx> wrote: > > On 2/22/2023 7:18 PM, Pasha Tatashin wrote: > > Hi Pasha, > > >> Coming from the virtio-pmem and some free page hinting background, I am > >> interested in this discussion. I saw your proposal about single owner > >> memory driver in other thread and could not entirely link the dots about > >> applicability of the idea with "reducing the memory footprint overhead > >> for virtual machines". Do we plan to co-ordinate guest memory state with > >> corresponding host state for efficient memory reclaim decisions? > >> Or something entirely different we are targeting here? > > > > Hi Pankaj, > > > > The plan is to have a driver /dev/memctl and corresponding VMM agent > > that synchronously passes information about how guest would like its > > memory to be backed on the host. > > > > For example the following information can come from guest for a range > > of physical addresses: > > MADV_NOHUGEPAGE > > MADV_HUGEPAGE > > MADV_DONTNEED > > PR_SET_VMA_ANON_NAME > > etc. > > > > All together this should help by doing memory management operations > > only on the host side, and reduce the number of operations that are > > performed on the guest. > > o.k. That sounds like guest will have a *special* interface (paravirt?) > for some of the memory management operations with the coordination of host. That is correct, hence memory passthrough. > > Guest would still allow other regular memory operations? which would get > full-filled by the guest? Just wondering if this solution only be > useful for specific workloads which are aware of known MADV calls? Depending on the flexibility of the interface, we are currently working supporting tcmalloc(), and also mmap(MAP_ANONYMOUS), but in the future can be extended to more types of memory. > And might not do/require continuous allocation/deallocation of memory? Contiguous memory allocation on the host is not required. Thanks, Pasha
