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SubjectRe: [PATCH 4/4] selftests: KVM: use dirty logging to check if page stats work correctly
On Sun, Mar 20, 2022 at 5:26 PM Mingwei Zhang <mizhang@google.com> wrote:
>
> When dirty logging is enabled, KVM splits the all hugepage mapping in
> NPT/EPT into the smallest 4K size. This property could be used to check if
> the page stats metrics work properly in KVM mmu. At the same time, this
> logic might be used the other way around: using page stats to verify if
> dirty logging really splits all huge pages. Moreover, when dirty logging is
> disabled, KVM zaps corresponding SPTEs and we could check whether the large
> pages come back when guest touches the pages again.
>
> So add page stats checking in dirty logging performance selftest. In
> particular, add checks in three locations:
> - just after vm is created;
> - after populating memory into vm but before enabling dirty logging;
> - just after turning on dirty logging.
> - after one final iteration after turning off dirty logging.
>
> Tested using commands:
> - ./dirty_log_perf_test -s anonymous_hugetlb_1gb
> - ./dirty_log_perf_test -s anonymous_thp
>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: David Matlack <dmatlack@google.com>
> Cc: Jing Zhang <jingzhangos@google.com>
> Cc: Peter Xu <peterx@redhat.com>
>
> Suggested-by: Ben Gardon <bgorden@google.com>

Woops, got a mail bounce from this. Should be:
Suggested-by: Ben Gardon <bgardon@google.com>

> Signed-off-by: Mingwei Zhang <mizhang@google.com>
> ---
> .../selftests/kvm/dirty_log_perf_test.c | 52 +++++++++++++++++++
> 1 file changed, 52 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> index 1954b964d1cf..ab0457d91658 100644
> --- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> @@ -19,6 +19,10 @@
> #include "perf_test_util.h"
> #include "guest_modes.h"
>
> +#ifdef __x86_64__
> +#include "processor.h"
> +#endif
> +
> /* How many host loops to run by default (one KVM_GET_DIRTY_LOG for each loop)*/
> #define TEST_HOST_LOOP_N 2UL
>
> @@ -185,6 +189,14 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> p->slots, p->backing_src,
> p->partition_vcpu_memory_access);
>
> +#ifdef __x86_64__
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_4k") == 0,
> + "4K page is non zero");
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_2m") == 0,
> + "2M page is non zero");
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_1g") == 0,
> + "1G page is non zero");
> +#endif
> perf_test_set_wr_fract(vm, p->wr_fract);
>
> guest_num_pages = (nr_vcpus * guest_percpu_mem_size) >> vm_get_page_shift(vm);
> @@ -222,6 +234,16 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> pr_info("Populate memory time: %ld.%.9lds\n",
> ts_diff.tv_sec, ts_diff.tv_nsec);
>
> +#ifdef __x86_64__
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_4k") != 0,
> + "4K page is zero");
> + if (p->backing_src == VM_MEM_SRC_ANONYMOUS_THP)
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_2m") != 0,
> + "2M page is zero");
> + if (p->backing_src == VM_MEM_SRC_ANONYMOUS_HUGETLB_1GB)
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_1g") != 0,
> + "1G page is zero");
> +#endif
> /* Enable dirty logging */
> clock_gettime(CLOCK_MONOTONIC, &start);
> enable_dirty_logging(vm, p->slots);
> @@ -267,6 +289,14 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> iteration, ts_diff.tv_sec, ts_diff.tv_nsec);
> }
> }
> +#ifdef __x86_64__
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_4k") != 0,
> + "4K page is zero after dirty logging");
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_2m") == 0,
> + "2M page is non-zero after dirty logging");
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_1g") == 0,
> + "1G page is non-zero after dirty logging");
> +#endif
>
> /* Disable dirty logging */
> clock_gettime(CLOCK_MONOTONIC, &start);
> @@ -275,6 +305,28 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> pr_info("Disabling dirty logging time: %ld.%.9lds\n",
> ts_diff.tv_sec, ts_diff.tv_nsec);
>
> +#ifdef __x86_64__
> + /*
> + * Increment iteration to run the vcpus again to verify if huge pages
> + * come back.
> + */
> + iteration++;
> + pr_info("Starting the final iteration to verify page stats\n");
> +
> + for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
> + while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id])
> + != iteration)
> + ;
> + }
> +
> + if (p->backing_src == VM_MEM_SRC_ANONYMOUS_THP)
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_2m") != 0,
> + "2M page is zero");
> + if (p->backing_src == VM_MEM_SRC_ANONYMOUS_HUGETLB_1GB)
> + TEST_ASSERT(vm_get_single_stat(vm, "pages_1g") != 0,
> + "1G page is zero");
> +#endif
> +
> /* Tell the vcpu thread to quit */
> host_quit = true;
> perf_test_join_vcpu_threads(nr_vcpus);
> --
> 2.35.1.894.gb6a874cedc-goog
>

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