14 files changed, 150 insertions, 16 deletions
diff --git a/libartbase/base/variant_map.h b/libartbase/base/variant_map.h
index 581bc234cc..7349bbc046 100644
--- a/libartbase/base/variant_map.h
+++ b/libartbase/base/variant_map.h
@@ -229,6 +229,14 @@ struct VariantMap {
     return GetValuePtr(key);
   }
 
+  // Look up the value from the key and return the value wrapped in a std::optional. If it was not
+  // set in the map, return an empty std::optional.
+  template <typename TValue>
+  std::optional<TValue> GetOptional(const TKey<TValue>& key) const {
+    auto* ptr = Get(key);
+    return (ptr == nullptr) ? std::optional<TValue>{} : std::make_optional(*ptr);
+  }
+
   // Lookup the value from the key. If it was not set in the map, return the default value.
   // The default value is either the key's default, or TValue{} if the key doesn't have a default.
   template <typename TValue>
diff --git a/runtime/metrics/metrics.cc b/runtime/metrics/metrics.cc
index 81ae2b4dab..e85897b19e 100644
--- a/runtime/metrics/metrics.cc
+++ b/runtime/metrics/metrics.cc
@@ -16,12 +16,20 @@
 
 #include "metrics.h"
 
+#include <sstream>
+
+#include "android-base/file.h"
 #include "android-base/logging.h"
 #include "base/macros.h"
+#include "base/scoped_flock.h"
+#include "runtime.h"
+#include "runtime_options.h"
 
 #pragma clang diagnostic push
 #pragma clang diagnostic error "-Wconversion"
 
+using android::base::WriteStringToFd;
+
 namespace art {
 namespace metrics {
 
@@ -116,15 +124,15 @@ std::unique_ptr<MetricsReporter> MetricsReporter::Create(ReportingConfig config,
   std::unique_ptr<MetricsBackend> backend;
 
   // We can't use std::make_unique here because the MetricsReporter constructor is private.
-  return std::unique_ptr<MetricsReporter>{new MetricsReporter{config, metrics}};
+  return std::unique_ptr<MetricsReporter>{new MetricsReporter{std::move(config), metrics}};
 }
 
 MetricsReporter::MetricsReporter(ReportingConfig config, const ArtMetrics* metrics)
-    : config_{config}, metrics_{metrics} {}
+    : config_{std::move(config)}, metrics_{metrics} {}
 
 MetricsReporter::~MetricsReporter() {
   // If we are configured to report metrics, do one final report at the end.
-  if (config_.dump_to_logcat) {
+  if (config_.ReportingEnabled()) {
     LOG_STREAM(INFO) << "\n*** ART internal metrics ***\n\n";
     // LOG_STREAM(INFO) destroys the stream at the end of the statement, which makes it tricky pass
     // it to store as a field in StreamBackend. To get around this, we use an immediately-invoked
@@ -136,6 +144,31 @@ MetricsReporter::~MetricsReporter() {
     }(LOG_STREAM(INFO));
     LOG_STREAM(INFO) << "\n*** Done dumping ART internal metrics ***\n";
   }
+  if (config_.dump_to_file.has_value()) {
+    const auto& filename = config_.dump_to_file.value();
+    std::ostringstream stream;
+    StreamBackend backend{stream};
+    metrics_->ReportAllMetrics(&backend);
+
+    std::string error_message;
+    auto file{
+        LockedFile::Open(filename.c_str(), O_CREAT | O_WRONLY | O_APPEND, true, &error_message)};
+    if (file.get() == nullptr) {
+      LOG(WARNING) << "Could open metrics file '" << filename << "': " << error_message;
+    } else {
+      if (!WriteStringToFd(stream.str(), file.get()->Fd())) {
+        PLOG(WARNING) << "Error writing metrics to file";
+      }
+    }
+  }
+}
+
+ReportingConfig ReportingConfig::FromRuntimeArguments(const RuntimeArgumentMap& args) {
+  using M = RuntimeArgumentMap;
+  return {
+      .dump_to_logcat = args.Exists(M::WriteMetricsToLog),
+      .dump_to_file = args.GetOptional(M::WriteMetricsToFile),
+  };
 }
 
 }  // namespace metrics
diff --git a/runtime/metrics/metrics.h b/runtime/metrics/metrics.h
index 7156d576e0..a6e395559a 100644
--- a/runtime/metrics/metrics.h
+++ b/runtime/metrics/metrics.h
@@ -21,6 +21,7 @@
 
 #include <array>
 #include <atomic>
+#include <optional>
 #include <ostream>
 #include <string_view>
 #include <vector>
@@ -58,6 +59,10 @@
 // per metric.
 
 namespace art {
+
+class Runtime;
+struct RuntimeArgumentMap;
+
 namespace metrics {
 
 /**
@@ -340,9 +345,16 @@ class ArtMetrics {
 std::string DatumName(DatumId datum);
 
 struct ReportingConfig {
-  bool dump_to_logcat;
-  // TODO(eholk): this will grow to support other configurations, such as logging to a file, or
-  // statsd. There will also be options for reporting after a period of time, or at certain events.
+  static ReportingConfig FromRuntimeArguments(const RuntimeArgumentMap& args);
+
+  // Causes metrics to be written to the log, which makes them show up in logcat.
+  bool dump_to_logcat{false};
+
+  // If set, provides a file name to enable metrics logging to a file.
+  std::optional<std::string> dump_to_file;
+
+  // Returns whether any options are set that enables metrics reporting.
+  constexpr bool ReportingEnabled() const { return dump_to_logcat || dump_to_file.has_value(); }
 };
 
 // MetricsReporter handles periodically reporting ART metrics.
diff --git a/runtime/parsed_options.cc b/runtime/parsed_options.cc
index 508e697f7f..5b8c9d3bc1 100644
--- a/runtime/parsed_options.cc
+++ b/runtime/parsed_options.cc
@@ -395,7 +395,12 @@ std::unique_ptr<RuntimeParser> ParsedOptions::MakeParser(bool ignore_unrecognize
       .Define("-Xuse-stderr-logger")
           .IntoKey(M::UseStderrLogger)
       .Define("-Xwrite-metrics-to-log")
+          .WithHelp("Enables writing ART metrics to logcat")
           .IntoKey(M::WriteMetricsToLog)
+      .Define("-Xwrite-metrics-to-file=_")
+          .WithHelp("Enables writing ART metrics to the given file")
+          .WithType<std::string>()
+          .IntoKey(M::WriteMetricsToFile)
       .Define("-Xonly-use-system-oat-files")
           .IntoKey(M::OnlyUseSystemOatFiles)
       .Define("-Xverifier-logging-threshold=_")
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index ac3c39219e..568d500563 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -223,13 +223,6 @@ void CheckConstants() {
   CHECK_EQ(mirror::Array::kFirstElementOffset, mirror::Array::FirstElementOffset());
 }
 
-metrics::ReportingConfig ParseMetricsReportingConfig(const RuntimeArgumentMap& args) {
-  using M = RuntimeArgumentMap;
-  return {
-      .dump_to_logcat = args.Exists(M::WriteMetricsToLog),
-  };
-}
-
 }  // namespace
 
 Runtime::Runtime()
@@ -1716,8 +1709,7 @@ bool Runtime::Init(RuntimeArgumentMap&& runtime_options_in) {
   // Class-roots are setup, we can now finish initializing the JniIdManager.
   GetJniIdManager()->Init(self);
 
-  metrics_reporter_ =
-      metrics::MetricsReporter::Create(ParseMetricsReportingConfig(runtime_options), &metrics_);
+  InitMetrics(runtime_options);
 
   // Runtime initialization is largely done now.
   // We load plugins first since that can modify the runtime state slightly.
@@ -1817,6 +1809,13 @@ bool Runtime::Init(RuntimeArgumentMap&& runtime_options_in) {
   return true;
 }
 
+void Runtime::InitMetrics(const RuntimeArgumentMap& runtime_options) {
+  auto metrics_config = metrics::ReportingConfig::FromRuntimeArguments(runtime_options);
+  if (metrics_config.ReportingEnabled()) {
+    metrics_reporter_ = metrics::MetricsReporter::Create(metrics_config, GetMetrics());
+  }
+}
+
 bool Runtime::EnsurePluginLoaded(const char* plugin_name, std::string* error_msg) {
   // Is the plugin already loaded?
   for (const Plugin& p : plugins_) {
diff --git a/runtime/runtime.h b/runtime/runtime.h
index 7fd731eb0d..06f05a177e 100644
--- a/runtime/runtime.h
+++ b/runtime/runtime.h
@@ -980,6 +980,7 @@ class Runtime {
       SHARED_TRYLOCK_FUNCTION(true, Locks::mutator_lock_);
   void InitNativeMethods() REQUIRES(!Locks::mutator_lock_);
   void RegisterRuntimeNativeMethods(JNIEnv* env);
+  void InitMetrics(const RuntimeArgumentMap& runtime_options);
 
   void StartDaemonThreads();
   void StartSignalCatcher();
diff --git a/runtime/runtime_options.def b/runtime/runtime_options.def
index 4462de22f5..80ec30833f 100644
--- a/runtime/runtime_options.def
+++ b/runtime/runtime_options.def
@@ -185,5 +185,6 @@ RUNTIME_OPTIONS_KEY (bool,                PerfettoHprof,                  false)
 
 // Whether to dump ART metrics to logcat
 RUNTIME_OPTIONS_KEY (Unit,                WriteMetricsToLog)
+RUNTIME_OPTIONS_KEY (std::string,         WriteMetricsToFile)
 
 #undef RUNTIME_OPTIONS_KEY
diff --git a/test/2234-write-metrics-to-file/check b/test/2234-write-metrics-to-file/check
new file mode 100755
index 0000000000..b9040957f6
--- /dev/null
+++ b/test/2234-write-metrics-to-file/check
@@ -0,0 +1,34 @@
+#!/bin/bash
+#
+# Copyright (C) 2020 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Inputs:
+# $1: Test's expected standard output
+# $2: Test's actual standard output
+# $3: Test's expected standard error
+# $4: Test's actual standard error
+
+# Check that one of the metrics appears in stderr.
+grep 'ClassVerificationTotalTime' "$2" >/dev/null
+MSG_FOUND=$?
+
+if [[ $MSG_FOUND -ne 0 ]] ; then
+  # Print out the log and return with error.
+  cat "$2"
+  exit 1
+fi
+
+# Success.
+exit 0
diff --git a/test/2234-write-metrics-to-file/expected-stderr.txt b/test/2234-write-metrics-to-file/expected-stderr.txt
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/2234-write-metrics-to-file/expected-stderr.txt
diff --git a/test/2234-write-metrics-to-file/expected-stdout.txt b/test/2234-write-metrics-to-file/expected-stdout.txt
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/2234-write-metrics-to-file/expected-stdout.txt
diff --git a/test/2234-write-metrics-to-file/info.txt b/test/2234-write-metrics-to-file/info.txt
new file mode 100644
index 0000000000..d2e50dfde0
--- /dev/null
+++ b/test/2234-write-metrics-to-file/info.txt
@@ -0,0 +1 @@
+Checks that metrics can be written to a file.
diff --git a/test/2234-write-metrics-to-file/run b/test/2234-write-metrics-to-file/run
new file mode 100755
index 0000000000..d2ff292100
--- /dev/null
+++ b/test/2234-write-metrics-to-file/run
@@ -0,0 +1,19 @@
+#!/bin/bash
+#
+# Copyright (C) 2020 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Use /dev/stdout as the file so that buildbot can automatically grab the output for the check
+# script.
+exec ${RUN} $@ --runtime-option -Xwrite-metrics-to-file=/dev/stdout
diff --git a/test/2234-write-metrics-to-file/src/Main.java b/test/2234-write-metrics-to-file/src/Main.java
new file mode 100644
index 0000000000..0426192ab2
--- /dev/null
+++ b/test/2234-write-metrics-to-file/src/Main.java
@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+public class Main {
+  public static void main(String[] args) {
+  }
+}
diff --git a/test/knownfailures.json b/test/knownfailures.json
index 385db458a9..4c6976258b 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -1351,7 +1351,8 @@
         "description": ["Failing on RI. Needs further investigating."]
     },
     {
-        "tests": ["2232-write-metrics-to-log"],
+        "tests": ["2232-write-metrics-to-log",
+                  "2234-write-metrics-to-file"],
         "variant": "jvm",
         "description": ["RI does not support ART metrics."]
     },