[metrics] Add timer conveniences
This adds convenience timers for each of the metrics. The timer's can be
backed by a Counter, in which case the Counter will store cumulative
time elapsed, or by a Histogram, in which case the timer will increment
a bucket based on the time between a particular start/stop pair.
Timers can either be manually started and stopped, or can be used
automatically in an RAII manner.
Bug: 170149255
Test: m test-art-host-gtest-art_libartbase_tests
Change-Id: I4fc77e35f3e7b67c12fc004b72bf4fe177dc3151
diff --git a/libartbase/base/metrics.h b/libartbase/base/metrics.h
index 51ea66f..d403834 100644
--- a/libartbase/base/metrics.h
+++ b/libartbase/base/metrics.h
@@ -25,6 +25,7 @@
#include <string_view>
#include <vector>
+#include "android-base/logging.h"
#include "base/time_utils.h"
#pragma clang diagnostic push
@@ -131,19 +132,21 @@
class MetricsCounter {
public:
+ using value_t = uint64_t;
+
explicit constexpr MetricsCounter(uint64_t value = 0) : value_{value} {
// Ensure we do not have any unnecessary data in this class.
static_assert(sizeof(*this) == sizeof(uint64_t));
}
void AddOne() { Add(1u); }
- void Add(uint64_t value) { value_.fetch_add(value, std::memory_order::memory_order_relaxed); }
+ void Add(value_t value) { value_.fetch_add(value, std::memory_order::memory_order_relaxed); }
- uint64_t Value() const { return value_.load(std::memory_order::memory_order_relaxed); }
+ value_t Value() const { return value_.load(std::memory_order::memory_order_relaxed); }
private:
- std::atomic<uint64_t> value_;
- static_assert(std::atomic<uint64_t>::is_always_lock_free);
+ std::atomic<value_t> value_;
+ static_assert(std::atomic<value_t>::is_always_lock_free);
};
template <size_t num_buckets_, int64_t minimum_value_, int64_t maximum_value_>
@@ -152,6 +155,8 @@
static_assert(minimum_value_ < maximum_value_);
public:
+ using value_t = int64_t;
+
constexpr MetricsHistogram() : buckets_{} {
// Ensure we do not have any unnecessary data in this class.
static_assert(sizeof(*this) == sizeof(uint32_t) * num_buckets_);
@@ -192,6 +197,73 @@
};
/**
+ * AutoTimer simplifies time-based metrics collection.
+ *
+ * Several modes are supported. In the default case, the timer starts immediately and stops when it
+ * goes out of scope. Example:
+ *
+ * {
+ * AutoTimer timer{metric};
+ * DoStuff();
+ * // timer stops and updates metric automatically here.
+ * }
+ *
+ * You can also stop the timer early:
+ *
+ * timer.Stop();
+ *
+ * Finally, you can choose to not automatically start the timer at the beginning by passing false as
+ * the second argument to the constructor:
+ *
+ * AutoTimer timer{metric, false};
+ * DoNotTimeThis();
+ * timer.Start();
+ * TimeThis();
+ *
+ * Manually started timers will still automatically stop in the destructor, but they can be manually
+ * stopped as well.
+ *
+ * Note that AutoTimer makes calls to MicroTime(), so this may not be suitable on critical paths, or
+ * in cases where the counter needs to be started and stopped on different threads.
+ */
+template <typename Metric>
+class AutoTimer {
+ public:
+ explicit AutoTimer(Metric* metric, bool autostart = true)
+ : running_{false}, start_time_microseconds_{}, metric_{metric} {
+ if (autostart) {
+ Start();
+ }
+ }
+
+ ~AutoTimer() {
+ if (running_) {
+ Stop();
+ }
+ }
+
+ void Start() {
+ DCHECK(!running_);
+ running_ = true;
+ start_time_microseconds_ = MicroTime();
+ }
+
+ void Stop() {
+ DCHECK(running_);
+ uint64_t stop_time_microseconds = MicroTime();
+ running_ = false;
+
+ metric_->Add(
+ static_cast<typename Metric::value_t>(stop_time_microseconds - start_time_microseconds_));
+ }
+
+ private:
+ bool running_;
+ uint64_t start_time_microseconds_;
+ Metric* metric_;
+};
+
+/**
* This struct contains all of the metrics that ART reports.
*/
class ArtMetrics {
diff --git a/libartbase/base/metrics_test.cc b/libartbase/base/metrics_test.cc
index 54306d6..67ad313 100644
--- a/libartbase/base/metrics_test.cc
+++ b/libartbase/base/metrics_test.cc
@@ -67,6 +67,53 @@
EXPECT_EQ(6u, test_counter.Value());
}
+TEST_F(MetricsTest, CounterTimer) {
+ MetricsCounter test_counter;
+ {
+ AutoTimer timer{&test_counter};
+ // Sleep for 2µs so the counter will be greater than 0.
+ NanoSleep(2'000);
+ }
+ EXPECT_GT(test_counter.Value(), 0u);
+}
+
+TEST_F(MetricsTest, CounterTimerExplicitStop) {
+ MetricsCounter test_counter;
+ AutoTimer timer{&test_counter};
+ // Sleep for 2µs so the counter will be greater than 0.
+ NanoSleep(2'000);
+ timer.Stop();
+ EXPECT_GT(test_counter.Value(), 0u);
+}
+
+TEST_F(MetricsTest, CounterTimerExplicitStart) {
+ MetricsCounter test_counter;
+ {
+ AutoTimer timer{&test_counter, /*autostart=*/false};
+ // Sleep for 2µs so the counter will be greater than 0.
+ NanoSleep(2'000);
+ }
+ EXPECT_EQ(test_counter.Value(), 0u);
+
+ {
+ AutoTimer timer{&test_counter, /*autostart=*/false};
+ timer.Start();
+ // Sleep for 2µs so the counter will be greater than 0.
+ NanoSleep(2'000);
+ }
+ EXPECT_GT(test_counter.Value(), 0u);
+}
+
+TEST_F(MetricsTest, CounterTimerExplicitStartStop) {
+ MetricsCounter test_counter;
+ AutoTimer timer{&test_counter, /*autostart=*/false};
+ // Sleep for 2µs so the counter will be greater than 0.
+ timer.Start();
+ NanoSleep(2'000);
+ timer.Stop();
+ EXPECT_GT(test_counter.Value(), 0u);
+}
+
TEST_F(MetricsTest, DatumName) {
EXPECT_EQ("ClassVerificationTotalTime", DatumName(DatumId::kClassVerificationTotalTime));
}
@@ -171,6 +218,17 @@
metrics.ReportAllMetrics(&backend);
}
+TEST_F(MetricsTest, HistogramTimer) {
+ TestMetricsHistogram<1, 0, 100> test_histogram;
+ {
+ AutoTimer timer{&test_histogram};
+ // Sleep for 2µs so the counter will be greater than 0.
+ NanoSleep(2'000);
+ }
+
+ EXPECT_GT(test_histogram.GetBucketsForTest()[0], 0u);
+}
+
} // namespace metrics
} // namespace art
