Re: [RFC PATCH v2 2/7] KVM: selftests: Use flag CLOCK_MONOTONIC_RAW for timing

From: Andrew Jones
Date: Thu Feb 25 2021 - 13:56:37 EST

On Thu, Feb 25, 2021 at 01:59:35PM +0800, Yanan Wang wrote:
> In addition to function of CLOCK_MONOTONIC, flag CLOCK_MONOTONIC_RAW can
> also shield possiable impact of NTP, which can provide more robustness.

IIRC, this should include

Suggested-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

>
> Signed-off-by: Yanan Wang <wangyanan55@xxxxxxxxxx>
> ---
> tools/testing/selftests/kvm/demand_paging_test.c | 8 ++++----
> tools/testing/selftests/kvm/dirty_log_perf_test.c | 14 +++++++-------
> tools/testing/selftests/kvm/lib/test_util.c | 2 +-
> tools/testing/selftests/kvm/steal_time.c | 4 ++--
> 4 files changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
> index 5f7a229c3af1..efbf0c1e9130 100644
> --- a/tools/testing/selftests/kvm/demand_paging_test.c
> +++ b/tools/testing/selftests/kvm/demand_paging_test.c
> @@ -53,7 +53,7 @@ static void *vcpu_worker(void *data)
> vcpu_args_set(vm, vcpu_id, 1, vcpu_id);
> run = vcpu_state(vm, vcpu_id);
>
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
>
> /* Let the guest access its memory */
> ret = _vcpu_run(vm, vcpu_id);
> @@ -86,7 +86,7 @@ static int handle_uffd_page_request(int uffd, uint64_t addr)
> copy.len = perf_test_args.host_page_size;
> copy.mode = 0;
>
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
>
> r = ioctl(uffd, UFFDIO_COPY, &copy);
> if (r == -1) {
> @@ -123,7 +123,7 @@ static void *uffd_handler_thread_fn(void *arg)
> struct timespec start;
> struct timespec ts_diff;
>
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
> while (!quit_uffd_thread) {
> struct uffd_msg msg;
> struct pollfd pollfd[2];
> @@ -336,7 +336,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
>
> pr_info("Finished creating vCPUs and starting uffd threads\n");
>
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
>
> for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
> pthread_create(&vcpu_threads[vcpu_id], NULL, vcpu_worker,
> diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> index 04a2641261be..6cff4ccf9525 100644
> --- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> @@ -50,7 +50,7 @@ static void *vcpu_worker(void *data)
> while (!READ_ONCE(host_quit)) {
> int current_iteration = READ_ONCE(iteration);
>
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
> ret = _vcpu_run(vm, vcpu_id);
> ts_diff = timespec_elapsed(start);
>
> @@ -141,7 +141,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> iteration = 0;
> host_quit = false;
>
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
> for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
> vcpu_last_completed_iteration[vcpu_id] = -1;
>
> @@ -162,7 +162,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> ts_diff.tv_sec, ts_diff.tv_nsec);
>
> /* Enable dirty logging */
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
> vm_mem_region_set_flags(vm, PERF_TEST_MEM_SLOT_INDEX,
> KVM_MEM_LOG_DIRTY_PAGES);
> ts_diff = timespec_elapsed(start);
> @@ -174,7 +174,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> * Incrementing the iteration number will start the vCPUs
> * dirtying memory again.
> */
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
> iteration++;
>
> pr_debug("Starting iteration %d\n", iteration);
> @@ -189,7 +189,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> pr_info("Iteration %d dirty memory time: %ld.%.9lds\n",
> iteration, ts_diff.tv_sec, ts_diff.tv_nsec);
>
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
> kvm_vm_get_dirty_log(vm, PERF_TEST_MEM_SLOT_INDEX, bmap);
>
> ts_diff = timespec_elapsed(start);
> @@ -199,7 +199,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> iteration, ts_diff.tv_sec, ts_diff.tv_nsec);
>
> if (dirty_log_manual_caps) {
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
> kvm_vm_clear_dirty_log(vm, PERF_TEST_MEM_SLOT_INDEX, bmap, 0,
> host_num_pages);
>
> @@ -212,7 +212,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> }
>
> /* Disable dirty logging */
> - clock_gettime(CLOCK_MONOTONIC, &start);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &start);
> vm_mem_region_set_flags(vm, PERF_TEST_MEM_SLOT_INDEX, 0);
> ts_diff = timespec_elapsed(start);
> pr_info("Disabling dirty logging time: %ld.%.9lds\n",
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index 906c955384e2..c7c0627c6842 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -89,7 +89,7 @@ struct timespec timespec_elapsed(struct timespec start)
> {
> struct timespec end;
>
> - clock_gettime(CLOCK_MONOTONIC, &end);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &end);
> return timespec_sub(end, start);
> }
>
> diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
> index fcc840088c91..5bc582d3f2a2 100644
> --- a/tools/testing/selftests/kvm/steal_time.c
> +++ b/tools/testing/selftests/kvm/steal_time.c
> @@ -237,11 +237,11 @@ static void *do_steal_time(void *arg)
> {
> struct timespec ts, stop;
>
> - clock_gettime(CLOCK_MONOTONIC, &ts);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
> stop = timespec_add_ns(ts, MIN_RUN_DELAY_NS);
>
> while (1) {
> - clock_gettime(CLOCK_MONOTONIC, &ts);
> + clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
> if (timespec_to_ns(timespec_sub(ts, stop)) >= 0)
> break;
> }
> --
> 2.19.1
>