Rik van Riel wrote: > Jeremy Fitzhardinge wrote: >> The more complex host policy decisions of how to balance overall >> memory use system-wide are much in the same for both mechanisms. > Not at all. Page hinting is just an optimization to host swapping, where > IO can be avoided on many of the pages that hit the end of the LRU. > > No decisions have to be made at all about balancing memory use > between guests, it just happens through regular host LRU aging. When the host pages out a page belonging to guest A, then its making a policy decision on how large guest A should be compared to B. If the policy is a global LRU on all guest pages, then that's still a policy on guest sizes: the target size is a function of its working set, assuming that the working set is well modelled by LRU. I imagine that if the guest and host are both managing their pages with an LRU-like algorithm you'll get some nasty interactions, which page hinting tries to alleviate. > Automatic ballooning requires that something on the host figures > out how much memory each guest needs and sizes the guests > appropriately. All the proposed policies for that which I have > seen have some nasty corner cases or are simply very limited > in scope. Well, you could apply something equivalent to a global LRU: ask for more pages from guests who have the most unused pages. (I'm not saying that its necessarily a useful policy.) J _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization