Hi Nick, On Tue, Apr 06, 2010 at 11:10:24PM +1000, Nick Piggin wrote: > most cases, quite possibly hardware improvements like asids will > be more useful. ASID already exists, they're not about preventing a vmexit for every tlb flush or alternatively guest pagetable updates. In short NPT/EPT is to ASID are what x86-64 is to PAE, not the other way around. It simplifies things and speedup server workloads tremendously. ASID if you want it, then you've to put it in OS guest to manage or in regular linux on host regardless of virtualization on or off. Anyway hugetlbfs exists in linux way before virtualization ever exited, so I guess we should keep the virtualization talk aside for now to make everyone happy, I already once said in this thread this whole work has been done in a way not specific to virtualization, and let's focus on applications that have larger working set than gcc/vi/make/git and somebody should explain why exactly hugetlbfs is included in the 2.6.34 kernel if tlb miss cost doesn't matter, and why so much work keeps going in the hugetlbfs direction including the 1g page size and java runs on hugetlbfs, oracle runs on hugetlbfs, etc... tons of apps are using libhugetlbfs and hugetlbfs is growing like its own VM that eventually will be able to swap of its own. > I don't really agree with how virtualization problem is characterised. > Xen's way of doing memory virtualization maps directly to normal > hardware page tables so there doesn't seem like a fundamental > requirement for more memory accesses. Xen also takes advantage of NPT/EPT, when it does it sure has the same hardware runtime cost of KVM without hugepages, unless Xen or the guest or both are using hugepages somewhere and trimming the pte level from the shadow or guest pagetables. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>