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

"wangyanan (Y)" <wangyanan55@xxxxxxxxxx> · Fri, 26 Feb 2021 10:49:16 +0800

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@xxxxxxxxxx>

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

Thanks,

Yanan

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

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