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Thu, 16 Apr 2020 16:09:41 +0100 Date: Thu, 16 Apr 2020 16:09:39 +0100 From: Marc Zyngier To: Paolo Bonzini Subject: Re: [PATCH v2] KVM/arm64: Support enabling dirty log gradually in small chunks Message-ID: <20200416160939.7e9c1621@why> In-Reply-To: References: <20200413122023.52583-1-zhukeqian1@huawei.com> Organization: Approximate X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: pbonzini@redhat.com, zhukeqian1@huawei.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, james.morse@arm.com, julien.thierry.kdev@gmail.com, will@kernel.org, suzuki.poulose@arm.com, sean.j.christopherson@intel.com, jianjay.zhou@huawei.com, wanghaibin.wang@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: kvm@vger.kernel.org, Will Deacon , linux-kernel@vger.kernel.org, Sean Christopherson , Jay Zhou , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Wed, 15 Apr 2020 18:13:56 +0200 Paolo Bonzini 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 > > --- > > 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? Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm