@@ -4197,14 +4197,18 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
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.
@@ -4213,28 +4217,6 @@ 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.
@@ -4242,13 +4224,18 @@ 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))
+ ret = kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
+ batch += ret;
+
+ if (ret)
goto restart;
}
Zap at lease 10 pages before releasing mmu-lock to reduce the overload caused by requiring lock After the patch, kvm_zap_obsolete_pages can forward progress anyway, so update the comments [ It improves the case 0.6% ~ 1% that do kernel building meanwhile read PCI ROM. ] Note: i am not sure that "10" is the best speculative value, i just guessed that '10' can make vcpu do not spend long time on kvm_zap_obsolete_pages and do not cause mmu-lock too hungry. Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> --- arch/x86/kvm/mmu.c | 35 +++++++++++------------------------ 1 files changed, 11 insertions(+), 24 deletions(-)