Add benchmarks for heap size retrieval

Add benchmarks for mallinfo, and for retrieving RSS from
/proc/self/statm, since we're considering using these for GC
triggering.

Add some static linkage specifiers, after running into a build
problem due to a spurious conflict.

Bug: 111447610

Test: Ran benchmarks
Change-Id: Ie50d512294993882728c63ce51ec507590257d80

3 files changed, 102 insertions, 3 deletions

diff --git a/benchmarks/Android.bp b/benchmarks/Android.bp
index bf8b10daf..722395d4e 100644
--- a/benchmarks/Android.bp
+++ b/benchmarks/Android.bp
@@ -28,6 +28,7 @@ cc_defaults {
     srcs: [
         "bionic_benchmarks.cpp",
         "atomic_benchmark.cpp",
+        "get_heap_size_benchmark.cpp",
         "inttypes_benchmark.cpp",
         "malloc_benchmark.cpp",
         "math_benchmark.cpp",
diff --git a/benchmarks/atomic_benchmark.cpp b/benchmarks/atomic_benchmark.cpp
index dcea1c862..ea008d4f1 100644
--- a/benchmarks/atomic_benchmark.cpp
+++ b/benchmarks/atomic_benchmark.cpp
@@ -37,13 +37,13 @@
 // We assume that the compiler is not smart enough to optimize away fences in a single-threaded
 // program. If that changes, we'll need to add a second thread.
 
-volatile unsigned counter;
+static volatile unsigned counter;
 
 std::atomic<int> test_loc(0);
 
-volatile unsigned sink;
+static volatile unsigned sink;
 
-std::mutex mtx;
+static std::mutex mtx;
 
 void BM_atomic_empty(benchmark::State& state) {
   while (state.KeepRunning()) {
diff --git a/benchmarks/get_heap_size_benchmark.cpp b/benchmarks/get_heap_size_benchmark.cpp
new file mode 100644
index 000000000..c3680dc44
--- /dev/null
+++ b/benchmarks/get_heap_size_benchmark.cpp
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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.
+ */
+
+// This measures the time required to compute two different native heap size metrics that
+// we might use to guide GC triggering.
+
+#include <atomic>
+#include <err.h>
+#include <fcntl.h>
+#include <malloc.h>
+#include <pthread.h>
+#include <sched.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <benchmark/benchmark.h>
+#include "util.h"
+
+static volatile size_t sink;
+
+static constexpr int NTHREADS = 5;
+
+static std::atomic<int> thread_count;
+
+static void* thread_func(void* arg) {
+  *reinterpret_cast<void**>(arg) = malloc(17);
+  thread_count++;
+  return nullptr;
+}
+
+static void BM_mallinfo(benchmark::State& state) {
+  pthread_t t[NTHREADS];
+  void* object[NTHREADS];
+  // Create threads to populate thread-local arenas, if any.
+  thread_count = 0;
+  for (int i = 0; i < 5; i++) {
+    int res = pthread_create(t + i, NULL, thread_func, object + i);
+    if (res != 0) {
+      errx(1, "ERROR: pthread_create failed");
+    }
+  }
+  while (thread_count != NTHREADS) {
+    sched_yield();
+  }
+  for (auto _ : state) {
+    sink = mallinfo().uordblks;
+  }
+  for (int i = 0; i < 5; i++) {
+    int res = pthread_join(t[i], NULL);
+    if (res != 0) {
+      errx(1, "ERROR: pthread_join failed");
+    }
+    free(object[i]);
+  }
+}
+
+BIONIC_BENCHMARK(BM_mallinfo);
+
+static constexpr int BUF_SIZE = 100;
+
+static void BM_read_statm(benchmark::State& state) {
+  char buf[BUF_SIZE];
+  int statm_fd = open("/proc/self/statm", O_RDONLY);
+  if (statm_fd == -1) {
+    errx(1, "ERROR: Open failed");
+  }
+  for (auto _ : state) {
+    off_t result = lseek(statm_fd, 0 /* offset */, SEEK_SET);
+    if (result == (off_t) -1) {
+      errx(1, "ERROR: lseek to beginning failed");
+    }
+    ssize_t nread = read(statm_fd, buf, BUF_SIZE);
+    if (nread < 13 || nread > 50) {
+      errx(1, "ERROR: Implausible read result; result = %zd", nread);
+    }
+    // We should really add the parsing overhead for the result; but that should be < 100 nsecs
+    // if we tweak it enough.
+  }
+  if (close(statm_fd) == -1) {
+    errx(1, "ERROR: Close failed");
+  }
+}
+
+BIONIC_BENCHMARK(BM_read_statm);