2 files changed, 51 insertions, 6 deletions
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.