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KVM: MMU: large page support

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Create large pages mappings if the guest PTE's are marked as such and
the underlying memory is hugetlbfs backed.  If the largepage contains
write-protected pages, a large pte is not used.

Gives a consistent 2% improvement for data copies on ram mounted
filesystem, without NPT/EPT.

Anthony measures a 4% improvement on 4-way kernbench, with NPT.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Marcelo Tosatti
2008-02-23 11:44:30 -03:00
committed by Avi Kivity
parent 2e53d63acb
commit 05da45583d
6 changed files with 262 additions and 32 deletions
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25
virt/kvm/kvm_main.c
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@@ -212,9 +212,13 @@ static void kvm_free_physmem_slot(struct kvm_memory_slot *free,
if (!dont || free->dirty_bitmap != dont->dirty_bitmap)
vfree(free->dirty_bitmap);
if (!dont || free->lpage_info != dont->lpage_info)
vfree(free->lpage_info);
free->npages = 0;
free->dirty_bitmap = NULL;
free->rmap = NULL;
free->lpage_info = NULL;
}
void kvm_free_physmem(struct kvm *kvm)
@@ -324,6 +328,25 @@ int __kvm_set_memory_region(struct kvm *kvm,
new.user_alloc = user_alloc;
new.userspace_addr = mem->userspace_addr;
}
if (npages && !new.lpage_info) {
int largepages = npages / KVM_PAGES_PER_HPAGE;
if (npages % KVM_PAGES_PER_HPAGE)
largepages++;
if (base_gfn % KVM_PAGES_PER_HPAGE)
largepages++;
new.lpage_info = vmalloc(largepages * sizeof(*new.lpage_info));
if (!new.lpage_info)
goto out_free;
memset(new.lpage_info, 0, largepages * sizeof(*new.lpage_info));
if (base_gfn % KVM_PAGES_PER_HPAGE)
new.lpage_info[0].write_count = 1;
if ((base_gfn+npages) % KVM_PAGES_PER_HPAGE)
new.lpage_info[largepages-1].write_count = 1;
}
/* Allocate page dirty bitmap if needed */
if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) {
@@ -467,7 +490,7 @@ int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
}
EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);
static unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
{
struct kvm_memory_slot *slot;