Messages in this thread | | | From | "Maciej S. Szmigiero" <> | Subject | Re: [PATCH v5.5 24/30] KVM: Use interval tree to do fast hva lookup in memslots | Date | Fri, 12 Nov 2021 00:52:05 +0100 |
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On 04.11.2021 01:25, Sean Christopherson wrote: > From: Maciej S. Szmigiero <maciej.szmigiero@oracle.com> > > The current memslots implementation only allows quick binary search by gfn, > quick lookup by hva is not possible - the implementation has to do a linear > scan of the whole memslots array, even though the operation being performed > might apply just to a single memslot. > > This significantly hurts performance of per-hva operations with higher > memslot counts. > > Since hva ranges can overlap between memslots an interval tree is needed > for tracking them. > > Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com> > [sean: handle interval tree updates in kvm_replace_memslot()] > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/arm64/kvm/Kconfig | 1 + > arch/mips/kvm/Kconfig | 1 + > arch/powerpc/kvm/Kconfig | 1 + > arch/s390/kvm/Kconfig | 1 + > arch/x86/kvm/Kconfig | 1 + > include/linux/kvm_host.h | 3 ++ > virt/kvm/kvm_main.c | 60 +++++++++++++++++++++++++++++----------- > 7 files changed, 52 insertions(+), 16 deletions(-) > (..) > @@ -1262,22 +1274,32 @@ static void kvm_replace_memslot(struct kvm_memslots *slots, > struct kvm_memory_slot *new) > { > /* > - * Remove the old memslot from the hash list, copying the node data > - * would corrupt the list. > + * Remove the old memslot from the hash list and interval tree, copying > + * the node data would corrupt the structures. > */ > if (old) { > hash_del(&old->id_node); > + interval_tree_remove(&old->hva_node, &slots->hva_tree); > > if (!new) > return; > } > > - /* Copy the source *data*, not the pointer, to the destination. */ > - if (old) > + /* > + * Copy the source *data*, not the pointer, to the destination. If > + * @old is NULL, initialize @new's hva range. > + */ > + if (old) { > *new = *old; > + } else if (new) {
Unnecessary check - if "new" is NULL then the code will crash anyway accessing this pointer unconditionally...
> + new->hva_node.start = new->userspace_addr; > + new->hva_node.last = new->userspace_addr + > + (new->npages << PAGE_SHIFT) - 1; > + } > > /* (Re)Add the new memslot. */ > hash_add(slots->id_hash, &new->id_node, new->id); > + interval_tree_insert(&new->hva_node, &slots->hva_tree);
...in these two lines above.
Thanks, Maciej
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