linux-kernel - [PATCH v6 4/7] KVM: MMU: zap pages in batch

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Date:	Fri, 17 May 2013 05:12:59 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	gleb@...hat.com
Cc:	avi.kivity@...il.com, mtosatti@...hat.com, pbonzini@...hat.com,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Subject: [PATCH v6 4/7] KVM: MMU: zap pages in batch

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@...ux.vnet.ibm.com>
---
 arch/x86/kvm/mmu.c |   14 ++++++++++++--
 1 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 891ad2c..7ad0e50 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4207,14 +4207,18 @@ restart:
 	spin_unlock(&kvm->mmu_lock);
 }
 
+#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 batch = 0;
 
 restart:
 	list_for_each_entry_safe_reverse(sp, node,
 	      &kvm->arch.active_mmu_pages, link) {
+		int ret;
+
 		/*
 		 * No obsolete page exists before new created page since
 		 * active_mmu_pages is the FIFO list.
@@ -4252,10 +4256,16 @@ 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))
+		ret = kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
+		batch += ret;
+
+		if (ret)
 			goto restart;
 	}
 
-- 
1.7.7.6

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