Hi Paolo, On 2020/4/16 23:55, Paolo Bonzini wrote: > On 16/04/20 17:09, Marc Zyngier wrote: >> On Wed, 15 Apr 2020 18:13:56 +0200 >> Paolo Bonzini <[email protected]> wrote: >> >>> On 13/04/20 14:20, Keqian Zhu wrote: >>>> There is already support of enabling dirty log graually in small chunks >>>> for x86 in commit 3c9bd4006bfc ("KVM: x86: enable dirty log gradually in >>>> small chunks"). This adds support for arm64. >>>> >>>> x86 still writes protect all huge pages when DIRTY_LOG_INITIALLY_ALL_SET >>>> is eanbled. However, for arm64, both huge pages and normal pages can be >>>> write protected gradually by userspace. >>>> >>>> Under the Huawei Kunpeng 920 2.6GHz platform, I did some tests on 128G >>>> Linux VMs with different page size. The memory pressure is 127G in each >>>> case. The time taken of memory_global_dirty_log_start in QEMU is listed >>>> below: >>>> >>>> Page Size Before After Optimization >>>> 4K 650ms 1.8ms >>>> 2M 4ms 1.8ms >>>> 1G 2ms 1.8ms >>>> >>>> Besides the time reduction, the biggest income is that we will minimize >>>> the performance side effect (because of dissloving huge pages and marking >>>> memslots dirty) on guest after enabling dirty log. >>>> >>>> Signed-off-by: Keqian Zhu <[email protected]> >>>> --- >>>> Documentation/virt/kvm/api.rst | 2 +- >>>> arch/arm64/include/asm/kvm_host.h | 3 +++ >>>> virt/kvm/arm/mmu.c | 12 ++++++++++-- >>>> 3 files changed, 14 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/Documentation/virt/kvm/api.rst >>>> b/Documentation/virt/kvm/api.rst >>>> index efbbe570aa9b..0017f63fa44f 100644 >>>> --- a/Documentation/virt/kvm/api.rst >>>> +++ b/Documentation/virt/kvm/api.rst >>>> @@ -5777,7 +5777,7 @@ will be initialized to 1 when created. This also >>>> improves performance because >>>> dirty logging can be enabled gradually in small chunks on the first call >>>> to KVM_CLEAR_DIRTY_LOG. KVM_DIRTY_LOG_INITIALLY_SET depends on >>>> KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE (it is also only available on >>>> -x86 for now). >>>> +x86 and arm64 for now). >>>> >>>> KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 was previously available under the name >>>> KVM_CAP_MANUAL_DIRTY_LOG_PROTECT, but the implementation had bugs that >>>> make >>>> diff --git a/arch/arm64/include/asm/kvm_host.h >>>> b/arch/arm64/include/asm/kvm_host.h >>>> index 32c8a675e5a4..a723f84fab83 100644 >>>> --- a/arch/arm64/include/asm/kvm_host.h >>>> +++ b/arch/arm64/include/asm/kvm_host.h >>>> @@ -46,6 +46,9 @@ >>>> #define KVM_REQ_RECORD_STEAL KVM_ARCH_REQ(3) >>>> #define KVM_REQ_RELOAD_GICv4 KVM_ARCH_REQ(4) >>>> >>>> +#define KVM_DIRTY_LOG_MANUAL_CAPS (KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE >>>> | \ >>>> + KVM_DIRTY_LOG_INITIALLY_SET) >>>> + >>>> DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); >>>> >>>> extern unsigned int kvm_sve_max_vl; >>>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c >>>> index e3b9ee268823..1077f653a611 100644 >>>> --- a/virt/kvm/arm/mmu.c >>>> +++ b/virt/kvm/arm/mmu.c >>>> @@ -2265,8 +2265,16 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, >>>> * allocated dirty_bitmap[], dirty pages will be be tracked while the >>>> * memory slot is write protected. >>>> */ >>>> - if (change != KVM_MR_DELETE && mem->flags & KVM_MEM_LOG_DIRTY_PAGES) >>>> - kvm_mmu_wp_memory_region(kvm, mem->slot); >>>> + if (change != KVM_MR_DELETE && mem->flags & KVM_MEM_LOG_DIRTY_PAGES) { >>>> + /* >>>> + * If we're with initial-all-set, we don't need to write >>>> + * protect any pages because they're all reported as dirty. >>>> + * Huge pages and normal pages will be write protect gradually. >>>> + */ >>>> + if (!kvm_dirty_log_manual_protect_and_init_set(kvm)) { >>>> + kvm_mmu_wp_memory_region(kvm, mem->slot); >>>> + } >>>> + } >>>> } >>>> >>>> int kvm_arch_prepare_memory_region(struct kvm *kvm, >>>> >>> >>> Marc, what is the status of this patch? >> >> I just had a look at it. Is there any urgency for merging it? > > No, I thought I was still replying to the v1. Sorry that patch v1 is dropped. Because I realized that stage2 page tables will be unmapped during VM reboot, or they are not established soon after migration, so stage2 page tables can not be used to decide whether a page is needed to migrate.
Thanks, Keqian > > Paolo > > > . > _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
