From 58d2930f4ee335ab703d768cb0318331fc1bb62c Mon Sep 17 00:00:00 2001
From: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Date: Tue, 17 Mar 2015 16:19:58 +0900
Subject: [PATCH] KVM: Eliminate extra function calls in
kvm_get_dirty_log_protect()
When all bits in mask are not set,
kvm_arch_mmu_enable_log_dirty_pt_masked() has nothing to do. But since
it needs to be called from the generic code, it cannot be inlined, and
a few function calls, two when PML is enabled, are wasted.
Since it is common to see many pages remain clean, e.g. framebuffers can
stay calm for a long time, it is worth eliminating this overhead.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
virt/kvm/kvm_main.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 49900fc21f89c..ce7888a151284 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1053,9 +1053,11 @@ int kvm_get_dirty_log_protect(struct kvm *kvm,
mask = xchg(&dirty_bitmap[i], 0);
dirty_bitmap_buffer[i] = mask;
- offset = i * BITS_PER_LONG;
- kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot, offset,
- mask);
+ if (mask) {
+ offset = i * BITS_PER_LONG;
+ kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
+ offset, mask);
+ }
}
spin_unlock(&kvm->mmu_lock);
--
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