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| author |   Jay Zhou <jianjay.zhou@huawei.com> | 2020-02-27 09:32:27 +0800 |
|---|---|---|
| committer |   Paolo Bonzini <pbonzini@redhat.com> | 2020-03-16 17:57:37 +0100 |
| commit | 3c9bd4006bfc2dccda1823db61b3f470ef91cfaa (patch) | |
| tree | 914a3fee54c7c102dfa8b6fd289cd1d18b6db19c /include/linux/kvm_host.h | |
| parent | KVM: x86/mmu: Reuse the current root if possible for fast switch (diff) | |
| download | wireguard-linux-3c9bd4006bfc2dccda1823db61b3f470ef91cfaa.tar.xz wireguard-linux-3c9bd4006bfc2dccda1823db61b3f470ef91cfaa.zip | |
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 'include/linux/kvm_host.h')
| -rw-r--r-- | include/linux/kvm_host.h | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 4bd5251b4477..127cb086ba32 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -360,6 +360,10 @@ static inline unsigned long *kvm_second_dirty_bitmap(struct kvm_memory_slot *mem return memslot->dirty_bitmap + len / sizeof(*memslot->dirty_bitmap); } +#ifndef KVM_DIRTY_LOG_MANUAL_CAPS +#define KVM_DIRTY_LOG_MANUAL_CAPS KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE +#endif + struct kvm_s390_adapter_int { u64 ind_addr; u64 summary_addr; @@ -493,7 +497,7 @@ struct kvm { #endif long tlbs_dirty; struct list_head devices; - bool manual_dirty_log_protect; + u64 manual_dirty_log_protect; struct dentry *debugfs_dentry; struct kvm_stat_data **debugfs_stat_data; struct srcu_struct srcu; @@ -527,6 +531,11 @@ struct kvm { #define vcpu_err(vcpu, fmt, ...) \ kvm_err("vcpu%i " fmt, (vcpu)->vcpu_id, ## __VA_ARGS__) +static inline bool kvm_dirty_log_manual_protect_and_init_set(struct kvm *kvm) +{ + return !!(kvm->manual_dirty_log_protect & KVM_DIRTY_LOG_INITIALLY_SET); +} + static inline struct kvm_io_bus *kvm_get_bus(struct kvm *kvm, enum kvm_bus idx) { return srcu_dereference_check(kvm->buses[idx], &kvm->srcu, |