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Date:   Thu, 25 Feb 2021 19:54:30 +0100
From:   Andrew Jones <drjones@redhat.com>
To:     Yanan Wang <wangyanan55@huawei.com>
Cc:     kvm@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-kernel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        Ben Gardon <bgardon@google.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Ingo Molnar <mingo@kernel.org>, Peter Xu <peterx@redhat.com>,
        Marc Zyngier <maz@kernel.org>, wanghaibin.wang@huawei.com,
        yuzenghui@huawei.com
Subject: Re: [RFC PATCH v2 2/7] KVM: selftests: Use flag CLOCK_MONOTONIC_RAW
 for timing
Message-ID: <20210225185430.fgafepkqo42u2yci@kamzik.brq.redhat.com>
References: <20210225055940.18748-1-wangyanan55@huawei.com>
 <20210225055940.18748-3-wangyanan55@huawei.com>
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In-Reply-To: <20210225055940.18748-3-wangyanan55@huawei.com>
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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@redhat.com>

> 
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> ---
>  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
>