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([2001:b07:6468:f312:9066:4f2:9fbd:f90e]) by smtp.gmail.com with ESMTPSA id p7sm24315229wrf.31.2020.04.15.09.13.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Apr 2020 09:13:57 -0700 (PDT) Subject: Re: [PATCH v2] KVM/arm64: Support enabling dirty log gradually in small chunks To: Keqian Zhu , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu Cc: Marc Zyngier , James Morse , Julien Thierry , Will Deacon , Suzuki K Poulose , Sean Christopherson , Jay Zhou , wanghaibin.wang@huawei.com References: <20200413122023.52583-1-zhukeqian1@huawei.com> From: Paolo Bonzini Message-ID: Date: Wed, 15 Apr 2020 18:13:56 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200413122023.52583-1-zhukeqian1@huawei.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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? Paolo