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Commit 19526396 authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
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KVM: MMU: do not iterate over all VMs in mmu_shrink() 



mmu_shrink() needlessly iterates over all VMs even though it will not
attempt to free mmu pages from more than one on them. Fix that and also
check used mmu pages count outside of VM lock to skip inactive VMs faster.

Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent a6bb7929

arch/x86/kvm/mmu.c

+17 −10
Original line number Diff line number Diff line
@@ -3944,7 +3944,6 @@ static void kvm_mmu_remove_some_alloc_mmu_pages(struct kvm *kvm, 
static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)

{

	struct kvm *kvm;

	struct kvm *kvm_freed = NULL;

	int nr_to_scan = sc->nr_to_scan;



	if (nr_to_scan == 0)
@@ -3956,22 +3955,30 @@ static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc) 
		int idx;

		LIST_HEAD(invalid_list);



		/*

		 * n_used_mmu_pages is accessed without holding kvm->mmu_lock

		 * here. We may skip a VM instance errorneosly, but we do not

		 * want to shrink a VM that only started to populate its MMU

		 * anyway.

		 */

		if (kvm->arch.n_used_mmu_pages > 0) {

			if (!nr_to_scan--)

				break;

			continue;

		}



		idx = srcu_read_lock(&kvm->srcu);

		spin_lock(&kvm->mmu_lock);

		if (!kvm_freed && nr_to_scan > 0 &&

		    kvm->arch.n_used_mmu_pages > 0) {

			kvm_mmu_remove_some_alloc_mmu_pages(kvm,

							    &invalid_list);

			kvm_freed = kvm;

		}

		nr_to_scan--;



		kvm_mmu_remove_some_alloc_mmu_pages(kvm, &invalid_list);

		kvm_mmu_commit_zap_page(kvm, &invalid_list);



		spin_unlock(&kvm->mmu_lock);

		srcu_read_unlock(&kvm->srcu, idx);



		list_move_tail(&kvm->vm_list, &vm_list);

		break;

	}

	if (kvm_freed)

		list_move_tail(&kvm_freed->vm_list, &vm_list);



	raw_spin_unlock(&kvm_lock);