v1/__thread/timed_backoff_policy.h

0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H
0011 #define _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H
0012
0013 #include <__config>
0014
0015 #if _LIBCPP_HAS_THREADS
0016
0017 #  include <__chrono/duration.h>
0018 #  include <__thread/support.h>
0019
0020 #  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0021 #    pragma GCC system_header
0022 #  endif
0023
0024 _LIBCPP_BEGIN_NAMESPACE_STD
0025
0026 struct __libcpp_timed_backoff_policy {
0027   _LIBCPP_HIDE_FROM_ABI bool operator()(chrono::nanoseconds __elapsed) const {
0028     if (__elapsed > chrono::milliseconds(128))
0029       __libcpp_thread_sleep_for(chrono::milliseconds(8));
0030     else if (__elapsed > chrono::microseconds(64))
0031       __libcpp_thread_sleep_for(__elapsed / 2);
0032     else if (__elapsed > chrono::microseconds(4))
0033       __libcpp_thread_yield();
0034     else {
0035     } // poll
0036     return false;
0037   }
0038 };
0039
0040 _LIBCPP_END_NAMESPACE_STD
0041
0042 #endif // _LIBCPP_HAS_THREADS
0043
0044 #endif // _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H