* Rik van Riel <riel@xxxxxxxxxx> [2010-02-04 08:40:43]: > On 02/03/2010 11:12 PM, Balbir Singh wrote: > >* Rik van Riel<riel@xxxxxxxxxx> [2010-02-03 16:11:03]: > > > >>Currently KVM pretends that pages with EPT mappings never got > >>accessed. This has some side effects in the VM, like swapping > >>out actively used guest pages and needlessly breaking up actively > >>used hugepages. > >> > >>We can avoid those very costly side effects by emulating the > >>accessed bit for EPT PTEs, which should only be slightly costly > >>because pages pass through page_referenced infrequently. > > >Quite a clever implementation, one side effect is that one would see a > >larger number of minor faults with EPT enabled and an increase in > >allocation/frees of rmap entries, but that can be easily explained. > > I suspect it won't be very many. I have been monitoring > /proc/meminfo on my system while testing this patch, and > it is quite typical that the size of the inactive anon > list does not change for minutes at a time. > > In other words, no pages are moved onto or off of the > inactive anon list for several minutes. That corresponds > to a very small number of minor faults introduced by my > patch. > > Of course, when the system is swapping, we will have more > minor faults. However, minor faults should be less of a > performance issue than major faults :) > I do agree with you. -- Balbir -- 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
