diff options
Diffstat (limited to 'src/third_party/abseil-cpp-master/abseil-cpp/absl/base/internal/sysinfo.cc')
| -rw-r--r-- | src/third_party/abseil-cpp-master/abseil-cpp/absl/base/internal/sysinfo.cc | 93 |
1 files changed, 64 insertions, 29 deletions
diff --git a/src/third_party/abseil-cpp-master/abseil-cpp/absl/base/internal/sysinfo.cc b/src/third_party/abseil-cpp-master/abseil-cpp/absl/base/internal/sysinfo.cc index db41bacc844..4a3b205034a 100644 --- a/src/third_party/abseil-cpp-master/abseil-cpp/absl/base/internal/sysinfo.cc +++ b/src/third_party/abseil-cpp-master/abseil-cpp/absl/base/internal/sysinfo.cc @@ -4,7 +4,7 @@ // 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 +// 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, @@ -17,7 +17,6 @@ #include "absl/base/attributes.h" #ifdef _WIN32 -#include <shlwapi.h> #include <windows.h> #else #include <fcntl.h> @@ -40,6 +39,7 @@ #endif #include <string.h> + #include <cassert> #include <cstdint> #include <cstdio> @@ -51,17 +51,16 @@ #include <vector> #include "absl/base/call_once.h" +#include "absl/base/config.h" #include "absl/base/internal/raw_logging.h" #include "absl/base/internal/spinlock.h" #include "absl/base/internal/unscaledcycleclock.h" +#include "absl/base/thread_annotations.h" namespace absl { +ABSL_NAMESPACE_BEGIN namespace base_internal { -static once_flag init_system_info_once; -static int num_cpus = 0; -static double nominal_cpu_frequency = 1.0; // 0.0 might be dangerous. - static int GetNumCPUs() { #if defined(__myriad2__) return 1; @@ -76,16 +75,32 @@ static int GetNumCPUs() { #if defined(_WIN32) static double GetNominalCPUFrequency() { - DWORD data; - DWORD data_size = sizeof(data); - #pragma comment(lib, "shlwapi.lib") // For SHGetValue(). - if (SUCCEEDED( - SHGetValueA(HKEY_LOCAL_MACHINE, - "HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0", - "~MHz", nullptr, &data, &data_size))) { - return data * 1e6; // Value is MHz. +#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP) && \ + !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP) + // UWP apps don't have access to the registry and currently don't provide an + // API informing about CPU nominal frequency. + return 1.0; +#else +#pragma comment(lib, "advapi32.lib") // For Reg* functions. + HKEY key; + // Use the Reg* functions rather than the SH functions because shlwapi.dll + // pulls in gdi32.dll which makes process destruction much more costly. + if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, + "HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0", 0, + KEY_READ, &key) == ERROR_SUCCESS) { + DWORD type = 0; + DWORD data = 0; + DWORD data_size = sizeof(data); + auto result = RegQueryValueExA(key, "~MHz", 0, &type, + reinterpret_cast<LPBYTE>(&data), &data_size); + RegCloseKey(key); + if (result == ERROR_SUCCESS && type == REG_DWORD && + data_size == sizeof(data)) { + return data * 1e6; // Value is MHz. + } } return 1.0; +#endif // WINAPI_PARTITION_APP && !WINAPI_PARTITION_DESKTOP } #elif defined(CTL_HW) && defined(HW_CPU_FREQ) @@ -256,28 +271,34 @@ static double GetNominalCPUFrequency() { #endif -// InitializeSystemInfo() may be called before main() and before -// malloc is properly initialized, therefore this must not allocate -// memory. -static void InitializeSystemInfo() { - num_cpus = GetNumCPUs(); - nominal_cpu_frequency = GetNominalCPUFrequency(); -} +ABSL_CONST_INIT static once_flag init_num_cpus_once; +ABSL_CONST_INIT static int num_cpus = 0; +// NumCPUs() may be called before main() and before malloc is properly +// initialized, therefore this must not allocate memory. int NumCPUs() { - base_internal::LowLevelCallOnce(&init_system_info_once, InitializeSystemInfo); + base_internal::LowLevelCallOnce( + &init_num_cpus_once, []() { num_cpus = GetNumCPUs(); }); return num_cpus; } +// A default frequency of 0.0 might be dangerous if it is used in division. +ABSL_CONST_INIT static once_flag init_nominal_cpu_frequency_once; +ABSL_CONST_INIT static double nominal_cpu_frequency = 1.0; + +// NominalCPUFrequency() may be called before main() and before malloc is +// properly initialized, therefore this must not allocate memory. double NominalCPUFrequency() { - base_internal::LowLevelCallOnce(&init_system_info_once, InitializeSystemInfo); + base_internal::LowLevelCallOnce( + &init_nominal_cpu_frequency_once, + []() { nominal_cpu_frequency = GetNominalCPUFrequency(); }); return nominal_cpu_frequency; } #if defined(_WIN32) pid_t GetTID() { - return GetCurrentThreadId(); + return pid_t{GetCurrentThreadId()}; } #elif defined(__linux__) @@ -325,15 +346,16 @@ pid_t GetTID() { #else // Fallback implementation of GetTID using pthread_getspecific. -static once_flag tid_once; -static pthread_key_t tid_key; -static absl::base_internal::SpinLock tid_lock( - absl::base_internal::kLinkerInitialized); +ABSL_CONST_INIT static once_flag tid_once; +ABSL_CONST_INIT static pthread_key_t tid_key; +ABSL_CONST_INIT static absl::base_internal::SpinLock tid_lock( + absl::kConstInit, base_internal::SCHEDULE_KERNEL_ONLY); // We set a bit per thread in this array to indicate that an ID is in // use. ID 0 is unused because it is the default value returned by // pthread_getspecific(). -static std::vector<uint32_t>* tid_array GUARDED_BY(tid_lock) = nullptr; +ABSL_CONST_INIT static std::vector<uint32_t> *tid_array + ABSL_GUARDED_BY(tid_lock) = nullptr; static constexpr int kBitsPerWord = 32; // tid_array is uint32_t. // Returns the TID to tid_array. @@ -400,5 +422,18 @@ pid_t GetTID() { #endif +// GetCachedTID() caches the thread ID in thread-local storage (which is a +// userspace construct) to avoid unnecessary system calls. Without this caching, +// it can take roughly 98ns, while it takes roughly 1ns with this caching. +pid_t GetCachedTID() { +#ifdef ABSL_HAVE_THREAD_LOCAL + static thread_local pid_t thread_id = GetTID(); + return thread_id; +#else + return GetTID(); +#endif // ABSL_HAVE_THREAD_LOCAL +} + } // namespace base_internal +ABSL_NAMESPACE_END } // namespace absl |