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 <xiaoguangr...@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

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