diff options
| author | Jay Zhou | 2020-02-27 09:32:27 +0800 |
|---|---|---|
| committer | Paolo Bonzini | 2020-03-16 17:57:37 +0100 |
| commit | 3c9bd4006bfc2dccda1823db61b3f470ef91cfaa (patch) | |
| tree | 914a3fee54c7c102dfa8b6fd289cd1d18b6db19c /arch/x86/kvm/mmu | |
| parent | 0be44352071dc87a4f9bf879642b1d44876971d9 (diff) | |
KVM: x86: enable dirty log gradually in small chunks
It could take kvm->mmu_lock for an extended period of time when
enabling dirty log for the first time. The main cost is to clear
all the D-bits of last level SPTEs. This situation can benefit from
manual dirty log protect as well, which can reduce the mmu_lock
time taken. The sequence is like this:
1. Initialize all the bits of the dirty bitmap to 1 when enabling
dirty log for the first time
2. Only write protect the huge pages
3. KVM_GET_DIRTY_LOG returns the dirty bitmap info
4. KVM_CLEAR_DIRTY_LOG will clear D-bit for each of the leaf level
SPTEs gradually in small chunks
Under the Intel(R) Xeon(R) Gold 6152 CPU @ 2.10GHz environment,
I did some tests with a 128G windows VM and counted the time taken
of memory_global_dirty_log_start, here is the numbers:
VM Size Before After optimization
128G 460ms 10ms
Signed-off-by: Jay Zhou <jianjay.zhou@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/mmu')
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 53b776dfc949..db0b66e153a2 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5864,13 +5864,14 @@ static bool slot_rmap_write_protect(struct kvm *kvm, } void kvm_mmu_slot_remove_write_access(struct kvm *kvm, - struct kvm_memory_slot *memslot) + struct kvm_memory_slot *memslot, + int start_level) { bool flush; spin_lock(&kvm->mmu_lock); - flush = slot_handle_all_level(kvm, memslot, slot_rmap_write_protect, - false); + flush = slot_handle_level(kvm, memslot, slot_rmap_write_protect, + start_level, PT_MAX_HUGEPAGE_LEVEL, false); spin_unlock(&kvm->mmu_lock); /* |