| Message ID | 20210225055940.18748-1-wangyanan55@huawei.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Some improvement and a new test for kvm page table | expand |
On Wed, Feb 24, 2021 at 9:59 PM Yanan Wang <wangyanan55@huawei.com> wrote: > > Hi, > This v2 series can mainly include two parts. > Based on kvm queue branch: https://git.kernel.org/pub/scm/virt/kvm/kvm.git/log/?h=queue > Links of v1: https://lore.kernel.org/lkml/20210208090841.333724-1-wangyanan55@huawei.com/ > > In the first part, all the known hugetlb backing src types specified > with different hugepage sizes are listed, so that we can specify use > of hugetlb source of the exact granularity that we want, instead of > the system default ones. And as all the known hugetlb page sizes are > listed, it's appropriate for all architectures. Besides, a helper that > can get granularity of different backing src types(anonumous/thp/hugetlb) > is added, so that we can use the accurate backing src granularity for > kinds of alignment or guest memory accessing of vcpus. > > In the second part, a new test is added: > This test is added to serve as a performance tester and a bug reproducer > for kvm page table code (GPA->HPA mappings), it gives guidance for the > people trying to make some improvement for kvm. And the following explains > what we can exactly do through this test. > > The function guest_code() can cover the conditions where a single vcpu or > multiple vcpus access guest pages within the same memory region, in three > VM stages(before dirty logging, during dirty logging, after dirty logging). > Besides, the backing src memory type(ANONYMOUS/THP/HUGETLB) of the tested > memory region can be specified by users, which means normal page mappings > or block mappings can be chosen by users to be created in the test. > > If ANONYMOUS memory is specified, kvm will create normal page mappings > for the tested memory region before dirty logging, and update attributes > of the page mappings from RO to RW during dirty logging. If THP/HUGETLB > memory is specified, kvm will create block mappings for the tested memory > region before dirty logging, and split the blcok mappings into normal page > mappings during dirty logging, and coalesce the page mappings back into > block mappings after dirty logging is stopped. > > So in summary, as a performance tester, this test can present the > performance of kvm creating/updating normal page mappings, or the > performance of kvm creating/splitting/recovering block mappings, > through execution time. > > When we need to coalesce the page mappings back to block mappings after > dirty logging is stopped, we have to firstly invalidate *all* the TLB > entries for the page mappings right before installation of the block entry, > because a TLB conflict abort error could occur if we can't invalidate the > TLB entries fully. We have hit this TLB conflict twice on aarch64 software > implementation and fixed it. As this test can imulate process from dirty > logging enabled to dirty logging stopped of a VM with block mappings, > so it can also reproduce this TLB conflict abort due to inadequate TLB > invalidation when coalescing tables. > > Links about the TLB conflict abort: > https://lore.kernel.org/lkml/20201201201034.116760-3-wangyanan55@huawei.com/ Besides a few style / readability comments, this series looks good to me. Thanks for generalizing the way these selftests handle different hugeTLB sizes! > > Yanan Wang (7): > tools include: sync head files of mmap flag encodings about hugetlb > KVM: selftests: Use flag CLOCK_MONOTONIC_RAW for timing > KVM: selftests: Make a generic helper to get vm guest mode strings > KVM: selftests: Add a helper to get system configured THP page size > KVM: selftests: List all hugetlb src types specified with page sizes > KVM: selftests: Adapt vm_userspace_mem_region_add to new helpers > KVM: selftests: Add a test for kvm page table code > > tools/include/asm-generic/hugetlb_encode.h | 3 + > tools/testing/selftests/kvm/Makefile | 3 + > .../selftests/kvm/demand_paging_test.c | 8 +- > .../selftests/kvm/dirty_log_perf_test.c | 14 +- > .../testing/selftests/kvm/include/kvm_util.h | 4 +- > .../testing/selftests/kvm/include/test_util.h | 21 +- > .../selftests/kvm/kvm_page_table_test.c | 476 ++++++++++++++++++ > tools/testing/selftests/kvm/lib/kvm_util.c | 58 +-- > tools/testing/selftests/kvm/lib/test_util.c | 92 +++- > tools/testing/selftests/kvm/steal_time.c | 4 +- > 10 files changed, 623 insertions(+), 60 deletions(-) > create mode 100644 tools/testing/selftests/kvm/kvm_page_table_test.c > > -- > 2.19.1 >