tweak rcu benchmarks

Summary:
Add a benchmark for `rcu_retire`. Remove perf code from the rcu tests.

As a motivating side-effect, removes faulty calls to `printf` which fail to compile across platforms, including mac.

Differential Revision: D27902852

fbshipit-source-id: 1698a0fd8ca3731f0b794cb1c2cb08c4bfb5d714

folly/synchronization/test/RcuBenchmark.cpp

@@ -19,23 +19,28 @@
 
 using namespace folly;
 
-void runTest(int iters) {
+BENCHMARK(RcuReader, iters) {
   BenchmarkSuspender susp;
 
   { rcu_reader g; }
   susp.dismiss();
 
   // run the test loop
-  for (int i = 0; i < iters; i++) {
+  while (iters--) {
     rcu_reader g;
   }
 }
 
-BENCHMARK_DRAW_LINE();
-BENCHMARK(RcuReader, iters) {
-  runTest(iters);
+BENCHMARK(RcuRetire, iters) {
+  BenchmarkSuspender susp;
+
+  rcu_retire<int>(nullptr, [](int*) {});
+  susp.dismiss();
+
+  while (iters--) {
+    rcu_retire<int>(nullptr, [](int*) {});
+  }
 }
-BENCHMARK_DRAW_LINE();
 
 int main(int argc, char* argv[]) {
   gflags::ParseCommandLineFlags(&argc, &argv, true);

folly/synchronization/test/RcuTest.cpp

@@ -53,32 +53,6 @@ TEST(RcuTest, Guard) {
   EXPECT_TRUE(del);
 }
 
-TEST(RcuTest, Perf) {
-  long i = FLAGS_iters;
-  auto start = std::chrono::steady_clock::now();
-  while (i-- > 0) {
-    rcu_reader g;
-  }
-  auto diff = std::chrono::steady_clock::now() - start;
-  printf(
-      "Total time %li ns \n",
-      std::chrono::duration_cast<std::chrono::nanoseconds>(diff).count() /
-          FLAGS_iters);
-}
-
-TEST(RcuTest, ResetPerf) {
-  long i = FLAGS_iters;
-  auto start = std::chrono::steady_clock::now();
-  while (i-- > 0) {
-    rcu_retire<int>(nullptr, [](int*) {});
-  }
-  auto diff = std::chrono::steady_clock::now() - start;
-  printf(
-      "Total time %li ns \n",
-      std::chrono::duration_cast<std::chrono::nanoseconds>(diff).count() /
-          FLAGS_iters);
-}
-
 TEST(RcuTest, SlowReader) {
   std::thread t;
   {