sysinfo.h (2702B)
1 // Copyright 2017 The Abseil Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 // This file includes routines to find out characteristics 16 // of the machine a program is running on. It is undoubtedly 17 // system-dependent. 18 19 // Functions listed here that accept a pid_t as an argument act on the 20 // current process if the pid_t argument is 0 21 // All functions here are thread-hostile due to file caching unless 22 // commented otherwise. 23 24 #ifndef ABSL_BASE_INTERNAL_SYSINFO_H_ 25 #define ABSL_BASE_INTERNAL_SYSINFO_H_ 26 27 #ifndef _WIN32 28 #include <sys/types.h> 29 #endif 30 31 #include <cstdint> 32 33 #include "absl/base/config.h" 34 #include "absl/base/port.h" 35 36 namespace absl { 37 ABSL_NAMESPACE_BEGIN 38 namespace base_internal { 39 40 // Nominal core processor cycles per second of each processor. This is _not_ 41 // necessarily the frequency of the CycleClock counter (see cycleclock.h) 42 // Thread-safe. 43 double NominalCPUFrequency(); 44 45 // Number of logical processors (hyperthreads) in system. Thread-safe. 46 int NumCPUs(); 47 48 // Return the thread id of the current thread, as told by the system. 49 // No two currently-live threads implemented by the OS shall have the same ID. 50 // Thread ids of exited threads may be reused. Multiple user-level threads 51 // may have the same thread ID if multiplexed on the same OS thread. 52 // 53 // On Linux, you may send a signal to the resulting ID with kill(). However, 54 // it is recommended for portability that you use pthread_kill() instead. 55 #ifdef _WIN32 56 // On Windows, process id and thread id are of the same type according to the 57 // return types of GetProcessId() and GetThreadId() are both DWORD, an unsigned 58 // 32-bit type. 59 using pid_t = uint32_t; 60 #endif 61 pid_t GetTID(); 62 63 // Like GetTID(), but caches the result in thread-local storage in order 64 // to avoid unnecessary system calls. Note that there are some cases where 65 // one must call through to GetTID directly, which is why this exists as a 66 // separate function. For example, GetCachedTID() is not safe to call in 67 // an asynchronous signal-handling context nor right after a call to fork(). 68 pid_t GetCachedTID(); 69 70 } // namespace base_internal 71 ABSL_NAMESPACE_END 72 } // namespace absl 73 74 #endif // ABSL_BASE_INTERNAL_SYSINFO_H_