Add a linker relocation benchmark

The benchmark creates a set of DSOs that mimic the work involved in
loading the current version of libandroid_servers.so. The synthetic
benchmark has roughly the same number of libraries with roughly the same
relocations.

Currently, on a local aosp_walleye build that includes recent performance
improvements (including the Neon-based CL
I3983bca1dddc9241bb70290ad3651d895f046660), using the "performance"
governor, the benchmark reports these scores:

$ adb shell taskset 10 \
  /data/benchmarktest64/linker-reloc-bench/linker-reloc-bench \
  --benchmark_repetitions=20 --benchmark_display_aggregates_only=true
...
--------------------------------------------------------------------------------
Benchmark                                      Time             CPU   Iterations
--------------------------------------------------------------------------------
BM_linker_relocation/real_time_mean        70048 us          465 us           20
BM_linker_relocation/real_time_median      70091 us          466 us           20
BM_linker_relocation/real_time_stddev        329 us         8.29 us           20

$ adb shell taskset 10 \
  /data/benchmarktest/linker-reloc-bench/linker-reloc-bench \
  --benchmark_repetitions=20 --benchmark_display_aggregates_only=true
...
--------------------------------------------------------------------------------
Benchmark                                      Time             CPU   Iterations
--------------------------------------------------------------------------------
BM_linker_relocation/real_time_mean        83051 us          462 us           20
BM_linker_relocation/real_time_median      83069 us          464 us           20
BM_linker_relocation/real_time_stddev        184 us         8.91 us           20

Test: manual
Bug: none
Change-Id: I6dac66978f8666f95c76387093bda6be0151bfce

1 files changed, 64 insertions, 0 deletions

diff --git a/benchmarks/spawn/spawn_benchmark.cpp b/benchmarks/spawn/spawn_benchmark.cpp
new file mode 100644
index 000000000..f2b5433a9
--- /dev/null
+++ b/benchmarks/spawn/spawn_benchmark.cpp
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "spawn_benchmark.h"
+
+#include <errno.h>
+#include <spawn.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <android-base/stringprintf.h>
+
+extern char** environ;
+
+void BM_spawn_test(benchmark::State& state, const char* const* argv) {
+  for (auto _ : state) {
+    pid_t child = 0;
+    if (int spawn_err = posix_spawn(&child, argv[0], nullptr, nullptr, const_cast<char**>(argv),
+                                    environ)) {
+      state.SkipWithError(android::base::StringPrintf(
+          "posix_spawn of %s failed: %s", argv[0], strerror(spawn_err)).c_str());
+      break;
+    }
+
+    int wstatus = 0;
+    const pid_t wait_result = TEMP_FAILURE_RETRY(waitpid(child, &wstatus, 0));
+    if (wait_result != child) {
+      state.SkipWithError(android::base::StringPrintf(
+          "waitpid on pid %d for %s failed: %s",
+          static_cast<int>(child), argv[0], strerror(errno)).c_str());
+      break;
+    }
+    if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 127) {
+      state.SkipWithError(android::base::StringPrintf("could not exec %s", argv[0]).c_str());
+      break;
+    }
+  }
+}