Paolo Bonzini <pbonz...@redhat.com> writes: > Il 13/06/2013 08:50, Eduardo Habkost ha scritto: >> I believe an interface based on guest physical memory addresses is more >> flexible (and even simpler!) than one that only allows binding of whole >> virtual NUMA nodes. > > And "-numa node" is already one, what about just adding "mem-path=/foo" > or "host_node=NN" suboptions? Then "-mem-path /foo" would be a shortcut > for "-numa node,mem-path=/foo". > > I even had patches to convert -numa to QemuOpts, I can dig them out if > your interested.
Ack. This is a very reasonable thing to add. Regards, Anthony Liguori > > Paolo > >> (And I still don't understand why you are exposing QEMU virtual memory >> addresses in the new command, if they are useless). >> >> >>>> >>>> >>>>>> * The correspondence between guest physical address ranges and ranges >>>>>> inside the mapped files (so external tools could set the policy on >>>>>> those files instead of requiring QEMU to set it directly) >>>>>> >>>>>> I understand that your use case may require additional information and >>>>>> additional interfaces. But if we provide the information above we will >>>>>> allow external components set the policy on the hugetlbfs files before >>>>>> we add new interfaces required for your use case. >>>>> >>>>> But the file backed memory is not good for the host which has many >>>>> virtual machines, in this situation, we can't handle anon THP yet. >>>> >>>> I don't understand what you mean, here. What prevents someone from using >>>> file-backed memory with multiple virtual machines? >>> >>> While if we use hugetlbfs backed memory, we should know how many virtual >>> machines, >>> how much memory each vm will use, then reserve these pages for them. And >>> even >>> should reserve more pages for external tools(numactl) to set memory polices. >>> Even the memory reservation also has it's own memory policies. It's very >>> hard >>> to control it to what we want to set. >> >> Well, it's hard because we don't even have tools to help on that, yet. >> >> Anyway, I understand that you want to make it work with THP as well. But >> if THP works with tmpfs (does it?), people then could use exactly the >> same file-based mechanisms with tmpfs and keep THP working. >> >> (Right now I am doing some experiments to understand how the system >> behaves when using numactl on hugetlbfs and tmpfs, before and after >> getting the files mapped). >> >> >>>> >>>>> >>>>> And as I mentioned, the cross numa node access performance regression >>>>> is caused by pci-passthrough, it's a very long time bug, we should >>>>> back port the host memory pinning patch to old QEMU to resolve this >>>>> performance >>>>> problem, too. >>>> >>>> If it's a regression, what's the last version of QEMU where the bug >>>> wasn't present? >>>> >>> >>> As QEMU doesn't support host memory binding, I think >>> this was present since we support guest NUMA, and the pci-passthrough made >>> it even worse. >> >> If the problem was always present, it is not a regression, is it? >>
