Record the present time once in Record() and pass that value to ViewInformation::Record(). (#36)

absl::Now() is remarkably expensive, and calling it for each ViewData was responsible for 6-8% of time spent in batched recording--after these changes total time in absl::Now() is negligible. (Log recording would move this off the critical path, but this would still help during log harvesting.)

Author: isturdy

opencensus/stats/BUILD

@@ -105,6 +105,7 @@ cc_library(
     deps = [
         ":core",
         "@com_google_absl//absl/strings",
+        "@com_google_absl//absl/time",
     ],
 )
 

opencensus/stats/internal/recording.cc

@@ -14,6 +14,7 @@
 
 #include "opencensus/stats/recording.h"
 
+#include "absl/time/clock.h"
 #include "opencensus/stats/internal/stats_manager.h"
 #include "opencensus/stats/measure.h"
 
@@ -24,7 +25,7 @@ void Record(
     std::initializer_list<Measurement> measurements,
     std::initializer_list<std::pair<absl::string_view, absl::string_view>>
         tags) {
-  StatsManager::Get()->Record(measurements, tags);
+  StatsManager::Get()->Record(measurements, tags, absl::Now());
 }
 
 }  // namespace stats

opencensus/stats/internal/stats_manager.cc

@@ -57,7 +57,8 @@ int StatsManager::ViewInformation::RemoveConsumer() {
 
 void StatsManager::ViewInformation::Record(
     double value,
-    absl::Span<const std::pair<absl::string_view, absl::string_view>> tags) {
+    absl::Span<const std::pair<absl::string_view, absl::string_view>> tags,
+    absl::Time now) {
   mu_->AssertHeld();
   std::vector<std::string> tag_values(descriptor_.columns().size());
   for (int i = 0; i < tag_values.size(); ++i) {
@@ -69,7 +70,7 @@ void StatsManager::ViewInformation::Record(
       }
     }
   }
-  data_.Add(value, tag_values, absl::Now());
+  data_.Add(value, tag_values, now);
 }
 
 ViewDataImpl StatsManager::ViewInformation::GetData() const {
@@ -86,10 +87,11 @@ ViewDataImpl StatsManager::ViewInformation::GetData() const {
 
 void StatsManager::MeasureInformation::Record(
     double value,
-    absl::Span<const std::pair<absl::string_view, absl::string_view>> tags) {
+    absl::Span<const std::pair<absl::string_view, absl::string_view>> tags,
+    absl::Time now) {
   mu_->AssertHeld();
   for (auto& view : views_) {
-    view->Record(value, tags);
+    view->Record(value, tags, now);
   }
 }
 
@@ -132,18 +134,18 @@ StatsManager* StatsManager::Get() {
 
 void StatsManager::Record(
     std::initializer_list<Measurement> measurements,
-    std::initializer_list<std::pair<absl::string_view, absl::string_view>>
-        tags) {
+    std::initializer_list<std::pair<absl::string_view, absl::string_view>> tags,
+    absl::Time now) {
   absl::MutexLock l(&mu_);
   for (const auto& measurement : measurements) {
     if (MeasureRegistryImpl::IdValid(measurement.id_)) {
       const uint64_t index = MeasureRegistryImpl::IdToIndex(measurement.id_);
       switch (MeasureRegistryImpl::IdToType(measurement.id_)) {
         case MeasureDescriptor::Type::kDouble:
-          measures_[index].Record(measurement.value_double_, tags);
+          measures_[index].Record(measurement.value_double_, tags, now);
           break;
         case MeasureDescriptor::Type::kInt64:
-          measures_[index].Record(measurement.value_int_, tags);
+          measures_[index].Record(measurement.value_int_, tags, now);
           break;
       }
     }

opencensus/stats/internal/stats_manager.h

@@ -18,6 +18,7 @@
 #include <memory>
 
 #include "absl/synchronization/mutex.h"
+#include "absl/time/time.h"
 #include "absl/types/span.h"
 #include "opencensus/common/internal/stats_object.h"
 #include "opencensus/stats/distribution.h"
@@ -56,7 +57,8 @@ class StatsManager final {
     // Requires holding *mu_.
     void Record(
         double value,
-        absl::Span<const std::pair<absl::string_view, absl::string_view>> tags);
+        absl::Span<const std::pair<absl::string_view, absl::string_view>> tags,
+        absl::Time now);
 
     // Retrieves a copy of the data.
     ViewDataImpl GetData() const LOCKS_EXCLUDED(*mu_);
@@ -85,7 +87,8 @@ class StatsManager final {
   void Record(
       std::initializer_list<Measurement> measurements,
       std::initializer_list<std::pair<absl::string_view, absl::string_view>>
-          tags) LOCKS_EXCLUDED(mu_);
+          tags,
+      absl::Time now) LOCKS_EXCLUDED(mu_);
 
   // Adds a measure--this is necessary for views to be added under that measure.
   template <typename MeasureT>
@@ -106,11 +109,13 @@ class StatsManager final {
    public:
     explicit MeasureInformation(absl::Mutex* mu) : mu_(mu) {}
 
-    // records 'value' against all views tracking 'measure'. Presently only
-    // supports doubles; recorded ints are converted to doubles internally.
+    // records 'value' against all views tracking 'measure' at time 'now'.
+    // Presently only supports doubles; recorded ints are converted to doubles
+    // internally.
     void Record(
         double value,
-        absl::Span<const std::pair<absl::string_view, absl::string_view>> tags);
+        absl::Span<const std::pair<absl::string_view, absl::string_view>> tags,
+        absl::Time now);
 
     ViewInformation* AddConsumer(const ViewDescriptor& descriptor);
     void RemoveView(const ViewInformation* handle);