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SubjectRe: [RFC V2 0/9] x86/mmu:Introduce parallel memory virtualization to boost performance
Any comments? Paolo! :)
On Wed, 9 Sep 2020 at 11:04, Wanpeng Li <kernellwp@gmail.com> wrote:
>
> Any comments? guys!
> On Tue, 1 Sep 2020 at 19:52, <yulei.kernel@gmail.com> wrote:
> >
> > From: Yulei Zhang <yulei.kernel@gmail.com>
> >
> > Currently in KVM memory virtulization we relay on mmu_lock to
> > synchronize the memory mapping update, which make vCPUs work
> > in serialize mode and slow down the execution, especially after
> > migration to do substantial memory mapping will cause visible
> > performance drop, and it can get worse if guest has more vCPU
> > numbers and memories.
> >
> > The idea we present in this patch set is to mitigate the issue
> > with pre-constructed memory mapping table. We will fast pin the
> > guest memory to build up a global memory mapping table according
> > to the guest memslots changes and apply it to cr3, so that after
> > guest starts up all the vCPUs would be able to update the memory
> > simultaneously without page fault exception, thus the performance
> > improvement is expected.
> >
> > We use memory dirty pattern workload to test the initial patch
> > set and get positive result even with huge page enabled. For example,
> > we create guest with 32 vCPUs and 64G memories, and let the vcpus
> > dirty the entire memory region concurrently, as the initial patch
> > eliminate the overhead of mmu_lock, in 2M/1G huge page mode we would
> > get the job done in about 50% faster.
> >
> > We only validate this feature on Intel x86 platform. And as Ben
> > pointed out in RFC V1, so far we disable the SMM for resource
> > consideration, drop the mmu notification as in this case the
> > memory is pinned.
> >
> > V1->V2:
> > * Rebase the code to kernel version 5.9.0-rc1.
> >
> > Yulei Zhang (9):
> > Introduce new fields in kvm_arch/vcpu_arch struct for direct build EPT
> > support
> > Introduce page table population function for direct build EPT feature
> > Introduce page table remove function for direct build EPT feature
> > Add release function for direct build ept when guest VM exit
> > Modify the page fault path to meet the direct build EPT requirement
> > Apply the direct build EPT according to the memory slots change
> > Add migration support when using direct build EPT
> > Introduce kvm module parameter global_tdp to turn on the direct build
> > EPT mode
> > Handle certain mmu exposed functions properly while turn on direct
> > build EPT mode
> >
> > arch/mips/kvm/mips.c | 13 +
> > arch/powerpc/kvm/powerpc.c | 13 +
> > arch/s390/kvm/kvm-s390.c | 13 +
> > arch/x86/include/asm/kvm_host.h | 13 +-
> > arch/x86/kvm/mmu/mmu.c | 533 ++++++++++++++++++++++++++++++--
> > arch/x86/kvm/svm/svm.c | 2 +-
> > arch/x86/kvm/vmx/vmx.c | 7 +-
> > arch/x86/kvm/x86.c | 55 ++--
> > include/linux/kvm_host.h | 7 +-
> > virt/kvm/kvm_main.c | 43 ++-
> > 10 files changed, 639 insertions(+), 60 deletions(-)
> >
> > --
> > 2.17.1
> >

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