On 03/03/2013 06:36 PM, KY Srinivasan wrote: >> I guess the most obvious question about exporting this symbol is, "Why >> doesn't any of the other hypervisor balloon drivers need this? What is >> so special about hyper-v?" > > The balloon protocol that Hyper-V has specified is designed around the ability to > move 2M pages. While the protocol can handle 4k allocations, it is going to be very chatty > with 4K allocations. What does "very chatty" mean? Do you think that there will be a noticeable performance difference ballooning 2M pages vs 4k? > Furthermore, the Memory Balancer on the host is also designed to work > best with memory moving around in 2M chunks. While I have not seen the code on the Windows > host that does this memory balancing, looking at how Windows guests behave in this environment, > (relative to Linux) I have to assume that the 2M allocations that Windows guests do are a big part of > the difference we see. You've been talking about differences. Could you elaborate on what the differences in behavior are that you are trying to rectify here? >> Or can those other drivers also need/use it as well, and they were just >> too chicken to be asking for the export? :) > > The 2M balloon allocations would make sense if the host is designed accordingly. How does the guest decide which size pages to allocate? It seems like a relatively bad idea to be inflating the balloon with 2M pages from the guest in the case where the guest is under memory pressure _and_ fragmented. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>