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authorIgor Mammedov <imammedo@redhat.com>2014-12-01 17:29:25 +0000
committerPaolo Bonzini <pbonzini@redhat.com>2014-12-04 15:29:10 +0100
commitd4ae84a02bc65cec29608bc417a969fc2ec75449 (patch)
treefdf2e5f189783ca5a47407c5a64dbea7f243e86a
parent7f379cff11fb9e00e0ff9eff8fbc39ddfd4b1bec (diff)
kvm: search_memslots: add simple LRU memslot caching
In typical guest boot workload only 2-3 memslots are used extensively, and at that it's mostly the same memslot lookup operation. Adding LRU cache improves average lookup time from 46 to 28 cycles (~40%) for this workload. Signed-off-by: Igor Mammedov <imammedo@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--include/linux/kvm_host.h12
1 files changed, 10 insertions, 2 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 231dd9472226..1a371447fd45 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -353,6 +353,7 @@ struct kvm_memslots {
struct kvm_memory_slot memslots[KVM_MEM_SLOTS_NUM];
/* The mapping table from slot id to the index in memslots[]. */
short id_to_index[KVM_MEM_SLOTS_NUM];
+ atomic_t lru_slot;
};
struct kvm {
@@ -790,12 +791,19 @@ static inline void kvm_guest_exit(void)
static inline struct kvm_memory_slot *
search_memslots(struct kvm_memslots *slots, gfn_t gfn)
{
- struct kvm_memory_slot *memslot;
+ int slot = atomic_read(&slots->lru_slot);
+ struct kvm_memory_slot *memslot = &slots->memslots[slot];
+
+ if (gfn >= memslot->base_gfn &&
+ gfn < memslot->base_gfn + memslot->npages)
+ return memslot;
kvm_for_each_memslot(memslot, slots)
if (gfn >= memslot->base_gfn &&
- gfn < memslot->base_gfn + memslot->npages)
+ gfn < memslot->base_gfn + memslot->npages) {
+ atomic_set(&slots->lru_slot, memslot - slots->memslots);
return memslot;
+ }
return NULL;
}