virtio — archive

[Rusty Russell <mst@redhat.com>]

"Michael S. Tsirkin" <mst@redhat.com> writes: > On Mon, Feb 03, 2014 at 01:37:17PM +1030, Rusty Russell wrote: >> "Michael S. Tsirkin" <mst@redhat.com> writes: >> > On Fri, Jan 31, 2014 at 04:01:39PM +1030, Rusty Russell wrote: >> >> The driver needs to explicitly ask for pages in that region. >> > >> > OK so we'll have an extra flag for that? >> >> No, I mean that the driver explicitly requests every page by PFN. If it >> requests a page in the extramem region, it will get one. > > Maybe I misunderstand. What is EXTRA_MEM is aid of? The VIRTIO_BALLOON_F_EXTRA_MEM feature enables the extra memory region. It's a simple form of memory hotplug. Daniel wanted it. It might make sense for some guests to allocate metadata (eg. array of struct pages) for that extra memory if it's required. > One other comment: for NUMA VMs we might want > to have separate counters for each node, > and separate memory pressure notification. > > Maybe just separate balloon for each node? Good question. We could add a range field in the config space, such that the different balloons cover different areas. On the other hand, we can add this in future with a feature bit. Though it would mean offering a guest multiple balloons, and then ignoring all but one if it didn't understand the range feature. Cheers, Rusty.