| Message ID | 20211115234603.2908381-1-bgardon@google.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Currently disabling dirty logging with the TDP MMU is extremely slow. On a 96 vCPU / 96G VM it takes ~45 seconds to disable dirty logging with the TDP MMU, as opposed to ~3.5 seconds with the legacy MMU. This series optimizes TLB flushes and intro | expand |
On Mon, Nov 15, 2021 at 3:46 PM Ben Gardon <bgardon@google.com> wrote: Haha oops, I lost the covers letter title there. It should have been "KVM: x86/mmu: Optimize disabling dirty logging" and the subject line should have been the first paragraph. I'll correct that on any future versions of this series I send out. > > Testing: > Ran KVM selftests and kvm-unit-tests on an Intel Skylake. This > series introduced no new failures. > > Performance: > To collect these results I needed to apply Mingwei's patch > "selftests: KVM: align guest physical memory base address to 1GB" > https://lkml.org/lkml/2021/8/29/310 > David Matlack is going to send out an updated version of that patch soon. > > Without this series, TDP MMU: > > ./dirty_log_perf_test -v 96 -s anonymous_hugetlb_1gb > Test iterations: 2 > Testing guest mode: PA-bits:ANY, VA-bits:48, 4K pages > guest physical test memory offset: 0x3fe7c0000000 > Populate memory time: 10.966500447s > Enabling dirty logging time: 0.002068737s > > Iteration 1 dirty memory time: 0.047556280s > Iteration 1 get dirty log time: 0.001253914s > Iteration 1 clear dirty log time: 0.049716661s > Iteration 2 dirty memory time: 3.679662016s > Iteration 2 get dirty log time: 0.000659546s > Iteration 2 clear dirty log time: 1.834329322s > Disabling dirty logging time: 45.738439510s > Get dirty log over 2 iterations took 0.001913460s. (Avg 0.000956730s/iteration) > Clear dirty log over 2 iterations took 1.884045983s. (Avg 0.942022991s/iteration) > > Without this series, Legacy MMU: > > ./dirty_log_perf_test -v 96 -s anonymous_hugetlb_1gb > Test iterations: 2 > Testing guest mode: PA-bits:ANY, VA-bits:48, 4K pages > guest physical test memory offset: 0x3fe7c0000000 > Populate memory time: 12.664750666s > Enabling dirty logging time: 0.002025510s > > Iteration 1 dirty memory time: 0.046240875s > Iteration 1 get dirty log time: 0.001864342s > Iteration 1 clear dirty log time: 0.170243637s > Iteration 2 dirty memory time: 31.571088701s > Iteration 2 get dirty log time: 0.000626245s > Iteration 2 clear dirty log time: 1.294817729s > Disabling dirty logging time: 3.566831573s > Get dirty log over 2 iterations took 0.002490587s. (Avg 0.001245293s/iteration) > Clear dirty log over 2 iterations took 1.465061366s. (Avg 0.732530683s/iteration) > > With this series, TDP MMU: > (Updated since RFC. Pulling out patches 1-4 could have a performance impact.) > > ./dirty_log_perf_test -v 96 -s anonymous_hugetlb_1gb > Test iterations: 2 > Testing guest mode: PA-bits:ANY, VA-bits:48, 4K pages > guest physical test memory offset: 0x3fe7c0000000 > Populate memory time: 12.225242366s > Enabling dirty logging time: 0.002063442s > > Iteration 1 dirty memory time: 0.047598123s > Iteration 1 get dirty log time: 0.001247702s > Iteration 1 clear dirty log time: 0.051062420s > Iteration 2 dirty memory time: 3.660439803s > Iteration 2 get dirty log time: 0.000736229s > Iteration 2 clear dirty log time: 1.043469951s > Disabling dirty logging time: 1.400549627s > Get dirty log over 2 iterations took 0.001983931s. (Avg 0.000991965s/iteration) > Clear dirty log over 2 iterations took 1.094532371s. (Avg 0.547266185s/iteration) > > Patch breakdown: > Patches 1 eliminates extra TLB flushes while disabling dirty logging. > Patches 2-8 remove the need for a vCPU pointer to make_spte > Patches 9-14 are small refactors in perparation for patch 19 > Patch 15 implements in-place largepage promotion when disabling dirty logging > > Changelog: > RFC -> v1: > Dropped the first 4 patches from the series. Patch 1 was sent > separately, patches 2-4 will be taken over by Sean Christopherson. > Incorporated David Matlack's Reviewed-by. > > Ben Gardon (15): > KVM: x86/mmu: Remove redundant flushes when disabling dirty logging > KVM: x86/mmu: Introduce vcpu_make_spte > KVM: x86/mmu: Factor wrprot for nested PML out of make_spte > KVM: x86/mmu: Factor mt_mask out of make_spte > KVM: x86/mmu: Remove need for a vcpu from > kvm_slot_page_track_is_active > KVM: x86/mmu: Remove need for a vcpu from mmu_try_to_unsync_pages > KVM: x86/mmu: Factor shadow_zero_check out of make_spte > KVM: x86/mmu: Replace vcpu argument with kvm pointer in make_spte > KVM: x86/mmu: Factor out the meat of reset_tdp_shadow_zero_bits_mask > KVM: x86/mmu: Propagate memslot const qualifier > KVM: x86/MMU: Refactor vmx_get_mt_mask > KVM: x86/mmu: Factor out part of vmx_get_mt_mask which does not depend > on vcpu > KVM: x86/mmu: Add try_get_mt_mask to x86_ops > KVM: x86/mmu: Make kvm_is_mmio_pfn usable outside of spte.c > KVM: x86/mmu: Promote pages in-place when disabling dirty logging > > arch/x86/include/asm/kvm-x86-ops.h | 1 + > arch/x86/include/asm/kvm_host.h | 2 + > arch/x86/include/asm/kvm_page_track.h | 6 +- > arch/x86/kvm/mmu/mmu.c | 45 +++++++------ > arch/x86/kvm/mmu/mmu_internal.h | 6 +- > arch/x86/kvm/mmu/page_track.c | 8 +-- > arch/x86/kvm/mmu/paging_tmpl.h | 6 +- > arch/x86/kvm/mmu/spte.c | 43 ++++++++---- > arch/x86/kvm/mmu/spte.h | 17 +++-- > arch/x86/kvm/mmu/tdp_mmu.c | 97 +++++++++++++++++++++------ > arch/x86/kvm/mmu/tdp_mmu.h | 5 +- > arch/x86/kvm/svm/svm.c | 8 +++ > arch/x86/kvm/vmx/vmx.c | 40 ++++++----- > include/linux/kvm_host.h | 10 +-- > virt/kvm/kvm_main.c | 12 ++-- > 15 files changed, 205 insertions(+), 101 deletions(-) > > -- > 2.34.0.rc1.387.gb447b232ab-goog >