| // Copyright 2017 The Abseil Authors. | |
| // | |
| // 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 | |
| // | |
| // https://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. | |
| // | |
| // This file includes routines to find out characteristics | |
| // of the machine a program is running on. It is undoubtedly | |
| // system-dependent. | |
| // Functions listed here that accept a pid_t as an argument act on the | |
| // current process if the pid_t argument is 0 | |
| // All functions here are thread-hostile due to file caching unless | |
| // commented otherwise. | |
| namespace absl { | |
| ABSL_NAMESPACE_BEGIN | |
| namespace base_internal { | |
| // Nominal core processor cycles per second of each processor. This is _not_ | |
| // necessarily the frequency of the CycleClock counter (see cycleclock.h) | |
| // Thread-safe. | |
| double NominalCPUFrequency(); | |
| // Number of logical processors (hyperthreads) in system. Thread-safe. | |
| int NumCPUs(); | |
| // Return the thread id of the current thread, as told by the system. | |
| // No two currently-live threads implemented by the OS shall have the same ID. | |
| // Thread ids of exited threads may be reused. Multiple user-level threads | |
| // may have the same thread ID if multiplexed on the same OS thread. | |
| // | |
| // On Linux, you may send a signal to the resulting ID with kill(). However, | |
| // it is recommended for portability that you use pthread_kill() instead. | |
| // On Windows, process id and thread id are of the same type according to the | |
| // return types of GetProcessId() and GetThreadId() are both DWORD, an unsigned | |
| // 32-bit type. | |
| using pid_t = uint32_t; | |
| pid_t GetTID(); | |
| // Like GetTID(), but caches the result in thread-local storage in order | |
| // to avoid unnecessary system calls. Note that there are some cases where | |
| // one must call through to GetTID directly, which is why this exists as a | |
| // separate function. For example, GetCachedTID() is not safe to call in | |
| // an asynchronous signal-handling context nor right after a call to fork(). | |
| pid_t GetCachedTID(); | |
| } // namespace base_internal | |
| ABSL_NAMESPACE_END | |
| } // namespace absl | |