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Subject: Re: [RFC PATCH v2 2/7] KVM: selftests: Use flag CLOCK_MONOTONIC_RAW
 for timing
To:     Andrew Jones <drjones@redhat.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>
References: <20210225055940.18748-1-wangyanan55@huawei.com>
 <20210225055940.18748-3-wangyanan55@huawei.com>
 <20210225185430.fgafepkqo42u2yci@kamzik.brq.redhat.com>
From:   "wangyanan (Y)" <wangyanan55@huawei.com>
Message-ID: <eca23409-21fc-b6d9-31b3-cab5eb703c98@huawei.com>
Date:   Fri, 26 Feb 2021 10:49:16 +0800
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On 2021/2/26 2:54, Andrew Jones wrote:
> 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>

Oh, sorry for my rashness. I will include it in v3.

Thanks,

Yanan

>> 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
>>
> .