[PATCH v5 8/8] KVM: MMU: zap pages in batch

[Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>]

Zap at lease 10 pages before releasing mmu-lock to reduce the overload
caused by requiring lock

[ It improves kernel building 0.6% ~ 1% ]

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
 arch/x86/kvm/mmu.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index e12f431..9c27fda 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4216,10 +4216,12 @@ restart:
 	spin_unlock(&kvm->mmu_lock);
 }
 
+#define BATCH_ZAP_PAGES	10
 static void zap_invalid_pages(struct kvm *kvm)
 {
 	struct kvm_mmu_page *sp, *node;
 	LIST_HEAD(invalid_list);
+	int batch = 0;
 
 restart:
 	list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
@@ -4256,11 +4258,14 @@ restart:
 		 * Need not flush tlb since we only zap the sp with invalid
 		 * generation number.
 		 */
-		if (cond_resched_lock(&kvm->mmu_lock))
+		if ((batch >= BATCH_ZAP_PAGES) &&
+		      cond_resched_lock(&kvm->mmu_lock)) {
+			batch = 0;
 			goto restart;
+		}
 
-		if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
-			goto restart;
+		batch += kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
+		goto restart;
 	}
 
 	/*
-- 
1.7.7.6