[PATCH 4/5] kvm: change memslot sorting rule from size to GFN

Igor Mammedov
2014-12-01T17:30:14Z

it will allow to use binary search for GFN -> memslot
lookups, reducing lookup cost with large slots amount.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
virt/kvm/kvm_main.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 278ed65..162817f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -666,10 +666,10 @@ static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot)
}

/*
- * Insert memslot and re-sort memslots based on their size,
- * so the larger slots will get better fit. Sorting algorithm
- * takes advantage of having initially sorted array and
- * known changed memslot position.
+ * Insert memslot and re-sort memslots based on their GFN,
+ * so binary search could be used to lookup GFN.
+ * Sorting algorithm takes advantage of having initially
+ * sorted array and known changed memslot position.
*/
static void update_memslots(struct kvm_memslots *slots,
struct kvm_memory_slot *new)
@@ -679,14 +679,19 @@ static void update_memslots(struct kvm_memslots *slots,
struct kvm_memory_slot *mslots = slots->memslots;

WARN_ON(mslots[i].id != id);
+ if (!new->npages)
+ new->base_gfn = 0;
+
while (i < KVM_MEM_SLOTS_NUM - 1 &&
- new->npages < mslots[i + 1].npages) {
+ new->base_gfn <= mslots[i + 1].base_gfn) {
+ if (!mslots[i + 1].npages)
+ break;
mslots[i] = mslots[i + 1];
slots->id_to_index[mslots[i].id] = i;
i++;
}
while (i > 0 &&
- new->npages > mslots[i - 1].npages) {
+ new->base_gfn > mslots[i - 1].base_gfn) {
mslots[i] = mslots[i - 1];
slots->id_to_index[mslots[i].id] = i;
i--;
--
1.8.3.1