Add some benchmarks for folly::coro::Task

Summary: Adds a few simple benchmarks to get an idea for the overhead of `folly::coro::Task` coroutines.

Reviewed By: yfeldblum

Differential Revision: D19729527

fbshipit-source-id: cdfbd5c408c24dd258c56bc159af0c03cb1cd55e

folly/experimental/coro/test/TaskBenchmark.cpp

+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * 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 <folly/Benchmark.h>
+#include <folly/Portability.h>
+
+#if FOLLY_HAS_COROUTINES
+
+#include <folly/experimental/coro/BlockingWait.h>
+#include <folly/experimental/coro/CurrentExecutor.h>
+#include <folly/experimental/coro/Task.h>
+
+#include <memory>
+
+BENCHMARK(SingleVoidSynchronousTaskInLoop, iters) {
+  folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
+    auto completeSynchronously = []() -> folly::coro::Task<void> { co_return; };
+    for (std::size_t i = 0; i < iters; ++i) {
+      co_await completeSynchronously();
+    }
+  }());
+}
+
+BENCHMARK(AsyncTaskInLoop, iters) {
+  folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
+    auto asyncReschedule = []() -> folly::coro::Task<void> {
+      co_await folly::coro::co_reschedule_on_current_executor;
+    };
+    for (std::size_t i = 0; i < iters; ++i) {
+      co_await asyncReschedule();
+    }
+  }());
+}
+
+BENCHMARK(AsyncRescheduleNoTask, iters) {
+  folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
+    for (std::size_t i = 0; i < iters; ++i) {
+      co_await folly::coro::co_reschedule_on_current_executor;
+    }
+  }());
+}
+
+class Base {
+ public:
+  virtual ~Base() {}
+
+  virtual folly::coro::Task<int> virtualMethod() = 0;
+};
+
+template <int Tag>
+class Derived : public Base {
+ public:
+  FOLLY_NOINLINE
+  folly::coro::Task<int> virtualMethod() override {
+    co_return Tag;
+  }
+};
+
+FOLLY_NOINLINE
+static std::unique_ptr<Base> makeBase(size_t iters) {
+  switch (iters % 3) {
+    case 0:
+      return std::make_unique<Derived<1>>();
+    case 1:
+      return std::make_unique<Derived<2>>();
+    default:
+      return std::make_unique<Derived<3>>();
+  }
+}
+
+BENCHMARK(VirtualTaskMethod, iters) {
+  folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
+    auto base = makeBase(iters);
+    size_t count = 0;
+    for (std::size_t i = 0; i < iters; ++i) {
+      count += co_await base->virtualMethod();
+    }
+    if (count != iters * ((iters % 3) + 1)) {
+      std::terminate();
+    }
+  }());
+}
+
+template <size_t N>
+static folly::coro::Task<void> staticNestedCalls() {
+  if constexpr (N > 0) {
+    co_await staticNestedCalls<N - 1>();
+  }
+  co_return;
+}
+
+template <size_t N>
+static void benchStaticNestedCalls(size_t iters) {
+  folly::coro::blockingWait([iters]() -> folly::coro::Task<void> {
+    for (size_t i = 0; i < iters; ++i) {
+      co_await staticNestedCalls<N>();
+    }
+  }());
+}
+
+BENCHMARK(StaticNestedCalls3, iters) {
+  benchStaticNestedCalls<3>(iters / 3);
+}
+
+BENCHMARK(StaticNestedCalls10, iters) {
+  benchStaticNestedCalls<10>(iters / 10);
+}
+
+static folly::coro::Task<void> nestedCalls(size_t depth) {
+  if (depth > 0) {
+    co_await nestedCalls(depth - 1);
+  }
+  co_return;
+}
+
+static void benchNestedCalls(size_t depth, size_t iters) {
+  folly::coro::blockingWait([depth, iters]() -> folly::coro::Task<void> {
+    for (size_t i = 0; i < iters; ++i) {
+      co_await nestedCalls(depth);
+    }
+  }());
+}
+
+BENCHMARK(NestedCalls3, iters) {
+  benchNestedCalls(3, iters / 3);
+}
+
+BENCHMARK(NestedCalls10, iters) {
+  benchNestedCalls(10, iters / 10);
+}
+
+static void benchNestedCallsWithCancellation(size_t depth, size_t iters) {
+  folly::CancellationSource cancelSource;
+  folly::coro::blockingWait(folly::coro::co_withCancellation(
+      cancelSource.getToken(), [depth, iters]() -> folly::coro::Task<void> {
+        for (size_t i = 0; i < iters; ++i) {
+          co_await nestedCalls(depth);
+        }
+      }()));
+}
+
+BENCHMARK(NestedCallsWithCancellation3, iters) {
+  benchNestedCallsWithCancellation(3, iters / 3);
+}
+
+BENCHMARK(NestedCallsWithCancellation10, iters) {
+  benchNestedCallsWithCancellation(10, iters / 10);
+}
+
+#endif // FOLLY_HAS_COROUTINES
+
+int main(int argc, char** argv) {
+  gflags::ParseCommandLineFlags(&argc, &argv, true);
+  folly::runBenchmarks();
+  return 0;
+}