On Thu, Mar 04, 2010 at 12:44:48AM +0100, Alexander Graf wrote: > > On 03.03.2010, at 20:12, Joerg Roedel wrote: > > > Hi, > > > > here are the patches that implement nested paging support for nested > > svm. They are somewhat intrusive to the soft-mmu so I post them as RFC > > in the first round to get feedback about the general direction of the > > changes. Nevertheless I am proud to report that with these patches the > > famous kernel-compile benchmark runs only 4% slower in the l2 guest as > > in the l1 guest when l2 is single-processor. With SMP guests the > > situation is very different. The more vcpus the guest has the more is > > the performance drop from l1 to l2. > > Anyway, this post is to get feedback about the overall concept of these > > patches. Please review and give feedback :-) > > Nice job! It's great to see you finally got around to it :-). > > Have you tracked what slows down SMP l2 guests yet? So far I've been > assuming that IPIs just completely kill the performance, but I guess > it shouldn't be that bad, especially now where you have sped up the > #VMEXIT path that much. I have not yet looked deeper into this issue. I also suspect lockholder preemption to be the cause for this. I did the test with a populated nested page table too and the slowdown is still there. But thats all guessing, I need to do some research for the exact reasons. Joerg -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
