1/*
2 * Copyright 2017-present Facebook, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#pragma once
18
19#include <folly/executors/thread_factory/ThreadFactory.h>
20
21#include <folly/String.h>
22#include <folly/portability/SysResource.h>
23#include <folly/portability/SysTime.h>
24
25namespace folly {
26
27/**
28 * A ThreadFactory that sets nice values for each thread. The main
29 * use case for this class is if there are multiple
30 * CPUThreadPoolExecutors in a single process, or between multiple
31 * processes, where some should have a higher priority than the others.
32 *
33 * Note that per-thread nice values are not POSIX standard, but both
34 * pthreads and linux support per-thread nice. The default linux
35 * scheduler uses these values to do smart thread prioritization.
36 * sched_priority function calls only affect real-time schedulers.
37 */
38class PriorityThreadFactory : public ThreadFactory {
39 public:
40 explicit PriorityThreadFactory(
41 std::shared_ptr<ThreadFactory> factory,
42 int priority)
43 : factory_(std::move(factory)), priority_(priority) {}
44
45 std::thread newThread(Func&& func) override {
46 int priority = priority_;
47 return factory_->newThread([priority, func = std::move(func)]() mutable {
48 if (setpriority(PRIO_PROCESS, 0, priority) != 0) {
49 LOG(ERROR) << "setpriority failed (are you root?) with error " << errno,
50 errnoStr(errno);
51 }
52 func();
53 });
54 }
55
56 private:
57 std::shared_ptr<ThreadFactory> factory_;
58 int priority_;
59};
60
61} // namespace folly
62