diff options
author | Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> | 2013-05-31 08:36:27 +0800 |
---|---|---|
committer | Gleb Natapov <gleb@redhat.com> | 2013-06-05 12:33:10 +0300 |
commit | e7d11c7a894986a13817c1c001e1e7668c5c4eb4 (patch) | |
tree | 73ef9501ae601f51c361ed71c1a419e84bc28c27 /arch/x86/kvm | |
parent | 7f52af7412275c0d23becfc325331ec8b5ff2458 (diff) | |
download | linux-e7d11c7a894986a13817c1c001e1e7668c5c4eb4.tar.bz2 |
KVM: MMU: zap pages in batch
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>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
-rw-r--r-- | arch/x86/kvm/mmu.c | 35 |
1 files changed, 11 insertions, 24 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 0880b9b425d7..fe9d6f10e7a9 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -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; } |