add pool_executor in pushmi/examples/pool.h, use it when updating the pushmi...

add pool_executor in pushmi/examples/pool.h, use it when updating the pushmi benchmark and migrating it to Folly.Benchmark

Summary: The PushmiBenchmark was badly bit-rotted. Update it for the latest pushmi design, migrate it to Folly.Benchmark, and implement it in terms of a new pushmi::pool_executor that is a thin wrapper over a pointer to a folly::CPUThreadPoolExecutor.

Reviewed By: kirkshoop

Differential Revision: D14550589

fbshipit-source-id: d808d6f5795ead421e6ee88439adb9ee652d3146

folly/experimental/pushmi/examples/pool.h

+/*
+ * Copyright 2018-present Facebook, Inc.
+ *
+ * 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.
+ */
+#pragma once
+
+#include <folly/experimental/pushmi/properties.h>
+#include <folly/experimental/pushmi/concepts.h>
+
+#include <folly/Executor.h>
+#include <folly/executors/CPUThreadPoolExecutor.h>
+
+namespace folly {
+namespace pushmi {
+
+class pool;
+
+class pool_executor {
+  struct task;
+  Executor::KeepAlive<CPUThreadPoolExecutor> exec_ {};
+
+public:
+  using properties =
+    property_set<is_executor<>, is_concurrent_sequence<>>;
+
+  pool_executor() = default;
+  explicit pool_executor(pool &e);
+  task schedule();
+};
+
+struct pool_executor::task {
+  using properties =
+    property_set<
+      is_sender<>, is_never_blocking<>, is_single<>>;
+
+  explicit task(pool_executor e)
+    : pool_ex_(std::move(e))
+  {}
+
+  PUSHMI_TEMPLATE(class Out)
+    (requires ReceiveValue<Out, pool_executor&>)
+  void submit(Out out) && {
+    pool_ex_.exec_->add([e = pool_ex_, out = std::move(out)]() mutable {
+      set_value(out, e);
+      set_done(out);
+    });
+  }
+private:
+  pool_executor pool_ex_;
+};
+
+class pool {
+  friend pool_executor;
+  CPUThreadPoolExecutor pool_;
+
+public:
+  explicit pool(std::size_t threads) : pool_(threads) {}
+
+  auto executor() {
+    return pool_executor{*this};
+  }
+
+  void stop() {
+    pool_.stop();
+  }
+
+  void wait() {
+    pool_.join();
+  }
+};
+
+inline pool_executor::pool_executor(pool &e)
+: exec_(Executor::getKeepAliveToken(e.pool_))
+{}
+
+inline pool_executor::task pool_executor::schedule() {
+  return task{*this};
+}
+
+} // namespace pushmi
+} // namespace folly