Add basic microbenchmarks.

PiperOrigin-RevId: 296104390

1 files changed, 149 insertions, 0 deletions

diff --git a/test/perf/linux/getdents_benchmark.cc b/test/perf/linux/getdents_benchmark.cc
new file mode 100644
index 000000000..0e03975b4
--- /dev/null
+++ b/test/perf/linux/getdents_benchmark.cc
@@ -0,0 +1,149 @@
+// 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 <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "gtest/gtest.h"
+#include "benchmark/benchmark.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/fs_util.h"
+#include "test/util/temp_path.h"
+#include "test/util/test_util.h"
+
+#ifndef SYS_getdents64
+#if defined(__x86_64__)
+#define SYS_getdents64 217
+#elif defined(__aarch64__)
+#define SYS_getdents64 217
+#else
+#error "Unknown architecture"
+#endif
+#endif  // SYS_getdents64
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+constexpr int kBufferSize = 16384;
+
+PosixErrorOr<TempPath> CreateDirectory(int count,
+                                       std::vector<std::string>* files) {
+  ASSIGN_OR_RETURN_ERRNO(TempPath dir, TempPath::CreateDir());
+
+  ASSIGN_OR_RETURN_ERRNO(FileDescriptor dfd,
+                         Open(dir.path(), O_RDONLY | O_DIRECTORY));
+
+  for (int i = 0; i < count; i++) {
+    auto file = NewTempRelPath();
+    auto res = MknodAt(dfd, file, S_IFREG | 0644, 0);
+    RETURN_IF_ERRNO(res);
+    files->push_back(file);
+  }
+
+  return std::move(dir);
+}
+
+PosixError CleanupDirectory(const TempPath& dir,
+                            std::vector<std::string>* files) {
+  ASSIGN_OR_RETURN_ERRNO(FileDescriptor dfd,
+                         Open(dir.path(), O_RDONLY | O_DIRECTORY));
+
+  for (auto it = files->begin(); it != files->end(); ++it) {
+    auto res = UnlinkAt(dfd, *it, 0);
+    RETURN_IF_ERRNO(res);
+  }
+  return NoError();
+}
+
+// Creates a directory containing `files` files, and reads all the directory
+// entries from the directory using a single FD.
+void BM_GetdentsSameFD(benchmark::State& state) {
+  // Create directory with given files.
+  const int count = state.range(0);
+
+  // Keep a vector of all of the file TempPaths that is destroyed before dir.
+  //
+  // Normally, we'd simply allow dir to recursively clean up the contained
+  // files, but that recursive cleanup uses getdents, which may be very slow in
+  // extreme benchmarks.
+  TempPath dir;
+  std::vector<std::string> files;
+  dir = ASSERT_NO_ERRNO_AND_VALUE(CreateDirectory(count, &files));
+
+  FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path(), O_RDONLY | O_DIRECTORY));
+  char buffer[kBufferSize];
+
+  // We read all directory entries on each iteration, but report this as a
+  // "batch" iteration so that reported times are per file.
+  while (state.KeepRunningBatch(count)) {
+    ASSERT_THAT(lseek(fd.get(), 0, SEEK_SET), SyscallSucceeds());
+
+    int ret;
+    do {
+      ASSERT_THAT(ret = syscall(SYS_getdents64, fd.get(), buffer, kBufferSize),
+                  SyscallSucceeds());
+    } while (ret > 0);
+  }
+
+  ASSERT_NO_ERRNO(CleanupDirectory(dir, &files));
+
+  state.SetItemsProcessed(state.iterations());
+}
+
+BENCHMARK(BM_GetdentsSameFD)->Range(1, 1 << 16)->UseRealTime();
+
+// Creates a directory containing `files` files, and reads all the directory
+// entries from the directory using a new FD each time.
+void BM_GetdentsNewFD(benchmark::State& state) {
+  // Create directory with given files.
+  const int count = state.range(0);
+
+  // Keep a vector of all of the file TempPaths that is destroyed before dir.
+  //
+  // Normally, we'd simply allow dir to recursively clean up the contained
+  // files, but that recursive cleanup uses getdents, which may be very slow in
+  // extreme benchmarks.
+  TempPath dir;
+  std::vector<std::string> files;
+  dir = ASSERT_NO_ERRNO_AND_VALUE(CreateDirectory(count, &files));
+  char buffer[kBufferSize];
+
+  // We read all directory entries on each iteration, but report this as a
+  // "batch" iteration so that reported times are per file.
+  while (state.KeepRunningBatch(count)) {
+    FileDescriptor fd =
+        ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path(), O_RDONLY | O_DIRECTORY));
+
+    int ret;
+    do {
+      ASSERT_THAT(ret = syscall(SYS_getdents64, fd.get(), buffer, kBufferSize),
+                  SyscallSucceeds());
+    } while (ret > 0);
+  }
+
+  ASSERT_NO_ERRNO(CleanupDirectory(dir, &files));
+
+  state.SetItemsProcessed(state.iterations());
+}
+
+BENCHMARK(BM_GetdentsNewFD)->Range(1, 1 << 16)->UseRealTime();
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor