On Mon, Mar 21, 2022 at 03:43:49PM -0700, Ben Gardon wrote: > Currently disabling dirty logging with the TDP MMU is extremely slow. > On a 96 vCPU / 96G VM it takes ~256 seconds to disable dirty logging > with the TDP MMU, as opposed to ~4 seconds with the legacy MMU. This > series optimizes TLB flushes and introduces in-place large page > promotion, to bring the disable dirty log time down to ~3 seconds. > > Testing: > Ran KVM selftests and kvm-unit-tests on an Intel Haswell. This > series introduced no new failures. > > Performance: > > 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: 4.972184425s > Enabling dirty logging time: 0.001943807s > > Iteration 1 dirty memory time: 0.061862112s > Iteration 1 get dirty log time: 0.001416413s > Iteration 1 clear dirty log time: 1.417428057s > Iteration 2 dirty memory time: 0.664103656s > Iteration 2 get dirty log time: 0.000676724s > Iteration 2 clear dirty log time: 1.149387201s > Disabling dirty logging time: 256.682188868s > Get dirty log over 2 iterations took 0.002093137s. (Avg 0.001046568s/iteration) > Clear dirty log over 2 iterations took 2.566815258s. (Avg 1.283407629s/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: 4.892940915s > Enabling dirty logging time: 0.001864603s > > Iteration 1 dirty memory time: 0.060490391s > Iteration 1 get dirty log time: 0.001416277s > Iteration 1 clear dirty log time: 0.323548614s > Iteration 2 dirty memory time: 29.217064826s > Iteration 2 get dirty log time: 0.000696202s > Iteration 2 clear dirty log time: 0.907089084s > Disabling dirty logging time: 4.246216551s > Get dirty log over 2 iterations took 0.002112479s. (Avg 0.001056239s/iteration) > Clear dirty log over 2 iterations took 1.230637698s. (Avg 0.615318849s/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: 4.878083336s > Enabling dirty logging time: 0.001874340s > > Iteration 1 dirty memory time: 0.054867383s > Iteration 1 get dirty log time: 0.001368377s > Iteration 1 clear dirty log time: 1.406960856s > Iteration 2 dirty memory time: 0.679301083s > Iteration 2 get dirty log time: 0.000662905s > Iteration 2 clear dirty log time: 1.138263359s > Disabling dirty logging time: 3.169381810s > Get dirty log over 2 iterations took 0.002031282s. (Avg 0.001015641s/iteration) > Clear dirty log over 2 iterations took 2.545224215s. (Avg 1.272612107s/iteration) > > Patch breakdown: > Patches 1-4 remove the need for a vCPU pointer to make_spte > Patches 5-8 are small refactors in preparation for in-place lpage promotion > Patch 9 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. > v1 -> v2: > Several patches were queued and dropped from this revision. > Incorporated feedback from Peter Xu on the last patch in the series. > Refreshed performance data > Between versions 1 and 2 of this series, disable time without > the TDP MMU went from 45s to 256, a major regression. I was > testing on a skylake before and haswell this time, but that > does not explain the huge performance loss. > > Ben Gardon (9): > KVM: x86/mmu: Move implementation of make_spte to a helper > KVM: x86/mmu: Factor mt_mask out of __make_spte > 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: 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 Use () after function names to make it clear you are referring to a function and not something else. e.g. KVM: x86/mmu: Move implementation of make_spte to a helper becomes KVM: x86/mmu: Move implementation of make_spte() to a helper This applies throughout the series, in commit messages and comments. > > arch/x86/include/asm/kvm-x86-ops.h | 1 + > arch/x86/include/asm/kvm_host.h | 2 + > arch/x86/kvm/mmu/mmu.c | 21 +++++---- > arch/x86/kvm/mmu/mmu_internal.h | 6 +++ > arch/x86/kvm/mmu/spte.c | 39 +++++++++++----- > arch/x86/kvm/mmu/spte.h | 6 +++ > arch/x86/kvm/mmu/tdp_mmu.c | 73 +++++++++++++++++++++++++++++- > arch/x86/kvm/svm/svm.c | 9 ++++ > arch/x86/kvm/vmx/vmx.c | 25 ++++++++-- > 9 files changed, 155 insertions(+), 27 deletions(-) > > -- > 2.35.1.894.gb6a874cedc-goog >
