Add basic microbenchmarks.

PiperOrigin-RevId: 296104390

1 files changed, 100 insertions, 0 deletions

diff --git a/test/perf/linux/randread_benchmark.cc b/test/perf/linux/randread_benchmark.cc
new file mode 100644
index 000000000..b0eb8c24e
--- /dev/null
+++ b/test/perf/linux/randread_benchmark.cc
@@ -0,0 +1,100 @@
+// Copyright 2020 The gVisor Authors.
+//
+// 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.
+
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+#include "gtest/gtest.h"
+#include "benchmark/benchmark.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/logging.h"
+#include "test/util/temp_path.h"
+#include "test/util/test_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+// Create a 1GB file that will be read from at random positions. This should
+// invalid any performance gains from caching.
+const uint64_t kFileSize = 1ULL << 30;
+
+// How many bytes to write at once to initialize the file used to read from.
+const uint32_t kWriteSize = 65536;
+
+// Largest benchmarked read unit.
+const uint32_t kMaxRead = 1UL << 26;
+
+TempPath CreateFile(uint64_t file_size) {
+  auto path = TempPath::CreateFile().ValueOrDie();
+  FileDescriptor fd = Open(path.path(), O_WRONLY).ValueOrDie();
+
+  // Try to minimize syscalls by using maximum size writev() requests.
+  std::vector<char> buffer(kWriteSize);
+  RandomizeBuffer(buffer.data(), buffer.size());
+  const std::vector<std::vector<struct iovec>> iovecs_list =
+      GenerateIovecs(file_size, buffer.data(), buffer.size());
+  for (const auto& iovecs : iovecs_list) {
+    TEST_CHECK(writev(fd.get(), iovecs.data(), iovecs.size()) >= 0);
+  }
+
+  return path;
+}
+
+// Global test state, initialized once per process lifetime.
+struct GlobalState {
+  const TempPath tmpfile;
+  explicit GlobalState(TempPath tfile) : tmpfile(std::move(tfile)) {}
+};
+
+GlobalState& GetGlobalState() {
+  // This gets created only once throughout the lifetime of the process.
+  // Use a dynamically allocated object (that is never deleted) to avoid order
+  // of destruction of static storage variables issues.
+  static GlobalState* const state =
+      // The actual file size is the maximum random seek range (kFileSize) + the
+      // maximum read size so we can read that number of bytes at the end of the
+      // file.
+      new GlobalState(CreateFile(kFileSize + kMaxRead));
+  return *state;
+}
+
+void BM_RandRead(benchmark::State& state) {
+  const int size = state.range(0);
+
+  GlobalState& global_state = GetGlobalState();
+  FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(global_state.tmpfile.path(), O_RDONLY));
+  std::vector<char> buf(size);
+
+  unsigned int seed = 1;
+  for (auto _ : state) {
+    TEST_CHECK(PreadFd(fd.get(), buf.data(), buf.size(),
+                       rand_r(&seed) % kFileSize) == size);
+  }
+
+  state.SetBytesProcessed(static_cast<int64_t>(size) *
+                          static_cast<int64_t>(state.iterations()));
+}
+
+BENCHMARK(BM_RandRead)->Range(1, kMaxRead)->UseRealTime();
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor