From fbb158cb88b6e4f8279707a1842ee0332f64b1a3 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 12 Sep 2019 19:46:07 -0700 Subject: KVM: x86/mmu: Revert "Revert "KVM: MMU: zap pages in batch"" Now that the fast invalidate mechanism has been reintroduced, restore the performance tweaks for fast invalidation that existed prior to its removal. Paraphrashing the original changelog: Zap at least 10 shadow pages before releasing mmu_lock to reduce the overhead associated with re-acquiring the lock. Note: "10" is an arbitrary number, speculated to be high enough so that a vCPU isn't stuck zapping obsolete pages for an extended period, but small enough so that other vCPUs aren't starved waiting for mmu_lock. This reverts commit 43d2b14b105fb00b8864c7b0ee7043cc1cc4a969. Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu.c | 35 +++++++++-------------------------- 1 file changed, 9 insertions(+), 26 deletions(-) (limited to 'arch/x86/kvm/mmu.c') diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 2ab0ac88d86e..3acc4b046d47 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -5671,12 +5671,12 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu) return ret; } - +#define BATCH_ZAP_PAGES 10 static void kvm_zap_obsolete_pages(struct kvm *kvm) { struct kvm_mmu_page *sp, *node; LIST_HEAD(invalid_list); - int ign; + int nr_zapped, batch = 0; restart: list_for_each_entry_safe_reverse(sp, node, @@ -5689,28 +5689,6 @@ restart: break; /* - * Do not repeatedly zap a root page to avoid unnecessary - * KVM_REQ_MMU_RELOAD, otherwise we may not be able to - * progress: - * vcpu 0 vcpu 1 - * call vcpu_enter_guest(): - * 1): handle KVM_REQ_MMU_RELOAD - * and require mmu-lock to - * load mmu - * repeat: - * 1): zap root page and - * send KVM_REQ_MMU_RELOAD - * - * 2): if (cond_resched_lock(mmu-lock)) - * - * 2): hold mmu-lock and load mmu - * - * 3): see KVM_REQ_MMU_RELOAD bit - * on vcpu->requests is set - * then return 1 to call - * vcpu_enter_guest() again. - * goto repeat; - * * Since we are reversely walking the list and the invalid * list will be moved to the head, skip the invalid page * can help us to avoid the infinity list walking. @@ -5718,14 +5696,19 @@ restart: if (sp->role.invalid) continue; - if (need_resched() || spin_needbreak(&kvm->mmu_lock)) { + if (batch >= BATCH_ZAP_PAGES && + (need_resched() || spin_needbreak(&kvm->mmu_lock))) { + batch = 0; kvm_mmu_commit_zap_page(kvm, &invalid_list); cond_resched_lock(&kvm->mmu_lock); goto restart; } - if (__kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &ign)) + if (__kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, + &nr_zapped)) { + batch += nr_zapped; goto restart; + } } kvm_mmu_commit_zap_page(kvm, &invalid_list); -- cgit v1.2.3