New arena benchmarks that actually hit the heap. (#275)

tests/benchmark.cc

@@ -9,15 +9,23 @@ upb_strview descriptor = google_protobuf_descriptor_proto_upbdefinit.descriptor;
 /* A buffer big enough to parse descriptor.proto without going to heap. */
 char buf[65535];
 
-static void BM_CreateArena(benchmark::State& state) {
+static void BM_CreateArenaNoHeap(benchmark::State& state) {
   for (auto _ : state) {
     upb_arena* arena = upb_arena_init(buf, sizeof(buf), NULL);
     upb_arena_free(arena);
   }
 }
+BENCHMARK(BM_CreateArenaNoHeap);
+
+static void BM_CreateArena(benchmark::State& state) {
+  for (auto _ : state) {
+    upb_arena* arena = upb_arena_new();
+    upb_arena_free(arena);
+  }
+}
 BENCHMARK(BM_CreateArena);
 
-static void BM_ParseDescriptor(benchmark::State& state) {
+static void BM_ParseDescriptorNoHeap(benchmark::State& state) {
   size_t bytes = 0;
   for (auto _ : state) {
     upb_arena* arena = upb_arena_init(buf, sizeof(buf), NULL);
@@ -33,4 +41,22 @@ static void BM_ParseDescriptor(benchmark::State& state) {
   }
   state.SetBytesProcessed(state.iterations() * descriptor.size);
 }
+BENCHMARK(BM_ParseDescriptorNoHeap);
+
+static void BM_ParseDescriptor(benchmark::State& state) {
+  size_t bytes = 0;
+  for (auto _ : state) {
+    upb_arena* arena = upb_arena_new();
+    google_protobuf_FileDescriptorProto* set =
+        google_protobuf_FileDescriptorProto_parse(descriptor.data,
+                                                descriptor.size, arena);
+    if (!set) {
+      printf("Failed to parse.\n");
+      exit(1);
+    }
+    bytes += descriptor.size;
+    upb_arena_free(arena);
+  }
+  state.SetBytesProcessed(state.iterations() * descriptor.size);
+}
 BENCHMARK(BM_ParseDescriptor);