Added README describing the directory.

benchmarks/README.md

+
+# Protocol Buffers Benchmarks
+
+This directory contains benchmarking schemas and data sets that you
+can use to test a variety of performance scenarios against your
+protobuf language runtime.
+
+The schema for the datasets is described in `benchmarks.proto`.
+
+Generate the data sets like so:
+
+```
+$ make
+$ ./generate-datasets
+Wrote dataset: dataset.google_message1_proto3.pb
+Wrote dataset: dataset.google_message1_proto2.pb
+Wrote dataset: dataset.google_message2.pb
+$
+```
+
+Each data set will be written to its own file.  Benchmarks will
+likely want to run several benchmarks against each data set (parse,
+serialize, possibly JSON, possibly using different APIs, etc).
+
+We would like to add more data sets.  In general we will favor data sets
+that make the overall suite diverse without being too large or having
+too many similar tests.  Ideally everyone can run through the entire
+suite without the test run getting too long.

benchmarks/benchmarks.proto

@@ -38,10 +38,12 @@ message BenchmarkDataset {
   string name = 1;
 
   // Fully-qualified name of the protobuf message for this dataset.
-  // It will be one of the messages defined benchmark_messages.proto.
+  // It will be one of the messages defined benchmark_messages_proto2.proto
+  // or benchmark_messages_proto3.proto.
+  //
   // Implementations that do not support reflection can implement this with
-  // an explicit "if/else" chain that lists every possible message defined
-  // in this file.
+  // an explicit "if/else" chain that lists every known message defined
+  // in those files.
   string message_name = 2;
 
   // The payload(s) for this dataset.  They should be parsed or serialized