From 12bc9994b427b60befac8bfd6a0c062963dc57e7 Mon Sep 17 00:00:00 2001
From: Ghanan Gowripalan <ghanan@google.com>
Date: Mon, 9 Oct 2023 10:15:33 -0700
Subject: [PATCH] Introduce select_benchmark

This benchmark performs similar measurements as epoll_benchmark.

PiperOrigin-RevId: 571972206
---
 test/perf/BUILD                     |   5 ++
 test/perf/linux/BUILD               |  18 +++++
 test/perf/linux/select_benchmark.cc | 100 ++++++++++++++++++++++++++++
 3 files changed, 123 insertions(+)
 create mode 100644 test/perf/linux/select_benchmark.cc

diff --git a/test/perf/BUILD b/test/perf/BUILD
index dff5241b5..2fb269307 100644
--- a/test/perf/BUILD
+++ b/test/perf/BUILD
@@ -31,6 +31,11 @@ syscall_test(
     test = "//test/perf/linux:poll_benchmark",
 )
 
+syscall_test(
+    debug = False,
+    test = "//test/perf/linux:select_benchmark",
+)
+
 syscall_test(
     size = "large",
     debug = False,
diff --git a/test/perf/linux/BUILD b/test/perf/linux/BUILD
index 1a7d1f062..a4a6502a0 100644
--- a/test/perf/linux/BUILD
+++ b/test/perf/linux/BUILD
@@ -287,6 +287,24 @@ cc_binary(
     ],
 )
 
+cc_binary(
+    name = "select_benchmark",
+    testonly = 1,
+    srcs = [
+        "select_benchmark.cc",
+    ],
+    deps = [
+        gbenchmark,
+        gtest,
+        "//test/util:eventfd_util",
+        "//test/util:file_descriptor",
+        "//test/util:posix_error",
+        "//test/util:test_main",
+        "//test/util:test_util",
+        "@com_google_absl//absl/time",
+    ],
+)
+
 cc_binary(
     name = "death_benchmark",
     testonly = 1,
diff --git a/test/perf/linux/select_benchmark.cc b/test/perf/linux/select_benchmark.cc
new file mode 100644
index 000000000..1b2a92ae6
--- /dev/null
+++ b/test/perf/linux/select_benchmark.cc
@@ -0,0 +1,100 @@
+// Copyright 2023 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/select.h>
+
+#include <cstdint>
+#include <utility>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "benchmark/benchmark.h"
+#include "test/util/eventfd_util.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/posix_error.h"
+#include "test/util/test_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+// Populates |event_fds| with new event FDs and |read_fds| with each new event
+// FD.
+void Setup(int count, std::vector<FileDescriptor>& event_fds, fd_set& read_fds,
+           int& max_fd) {
+  max_fd = -1;
+  for (int i = 0; i < count; ++i) {
+    FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(NewEventFD());
+    if (fd.get() > max_fd) {
+      max_fd = fd.get();
+    }
+    FD_SET(fd.get(), &read_fds);
+    event_fds.push_back(std::move(fd));
+  }
+}
+
+// Benchmarks a call to select(2) when no FD is "ready" with varying timeout
+// values.
+void BM_SelectTimeout(benchmark::State& state) {
+  constexpr int kFDsPerSelect = 3;
+  std::vector<FileDescriptor> event_fds;
+  fd_set read_fds;
+  int max_fd;
+  ASSERT_NO_FATAL_FAILURE(Setup(kFDsPerSelect, event_fds, read_fds, max_fd));
+
+  const int timeout_ms = state.range(0);
+  timeval timeout = {
+      .tv_sec = 0,
+      .tv_usec = timeout_ms * 1000,
+  };
+  for (auto _ : state) {
+    EXPECT_EQ(select(max_fd + 1, &read_fds, /*writefds=*/nullptr,
+                     /*exceptfds=*/nullptr, &timeout),
+              0);
+  }
+}
+
+BENCHMARK(BM_SelectTimeout)->Range(/*start=*/0, /*limit=*/8);
+
+// Benchmarks a call to select(2) with a zero timeout and varying number of
+// "ready" FDs.
+void BM_SelectAllEvents(benchmark::State& state) {
+  const int fds_per_select = state.range(0);
+  std::vector<FileDescriptor> event_fds;
+  fd_set read_fds;
+  int max_fd;
+  ASSERT_NO_FATAL_FAILURE(Setup(fds_per_select, event_fds, read_fds, max_fd));
+
+  constexpr uint64_t kEventVal = 5;
+  for (const auto& eventfd : event_fds) {
+    ASSERT_THAT(WriteFd(eventfd.get(), &kEventVal, sizeof(kEventVal)),
+                SyscallSucceedsWithValue(sizeof(kEventVal)));
+  }
+
+  timeval timeout = {};
+  for (auto _ : state) {
+    EXPECT_EQ(select(max_fd + 1, &read_fds, /*writefds=*/nullptr,
+                     /*exceptfds=*/nullptr, &timeout),
+              fds_per_select);
+  }
+}
+
+BENCHMARK(BM_SelectAllEvents)->Range(/*start=*/2, /*limit=*/1024);
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor