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Diffstat (limited to 'third_party/abseil_cpp/absl/base/internal/sysinfo.cc')
| -rw-r--r-- | third_party/abseil_cpp/absl/base/internal/sysinfo.cc | 425 |
1 files changed, 425 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/base/internal/sysinfo.cc b/third_party/abseil_cpp/absl/base/internal/sysinfo.cc new file mode 100644 index 000000000000..6c69683faf67 --- /dev/null +++ b/third_party/abseil_cpp/absl/base/internal/sysinfo.cc @@ -0,0 +1,425 @@ +// 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. + +#include "absl/base/internal/sysinfo.h" + +#include "absl/base/attributes.h" + +#ifdef _WIN32 +#include <windows.h> +#else +#include <fcntl.h> +#include <pthread.h> +#include <sys/stat.h> +#include <sys/types.h> +#include <unistd.h> +#endif + +#ifdef __linux__ +#include <sys/syscall.h> +#endif + +#if defined(__APPLE__) || defined(__FreeBSD__) +#include <sys/sysctl.h> +#endif + +#if defined(__myriad2__) +#include <rtems.h> +#endif + +#include <string.h> +#include <cassert> +#include <cstdint> +#include <cstdio> +#include <cstdlib> +#include <ctime> +#include <limits> +#include <thread> // NOLINT(build/c++11) +#include <utility> +#include <vector> + +#include "absl/base/call_once.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 int GetNumCPUs() { +#if defined(__myriad2__) + return 1; +#else + // Other possibilities: + // - Read /sys/devices/system/cpu/online and use cpumask_parse() + // - sysconf(_SC_NPROCESSORS_ONLN) + return std::thread::hardware_concurrency(); +#endif +} + +#if defined(_WIN32) + +static double GetNominalCPUFrequency() { +#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) + +static double GetNominalCPUFrequency() { + unsigned freq; + size_t size = sizeof(freq); + int mib[2] = {CTL_HW, HW_CPU_FREQ}; + if (sysctl(mib, 2, &freq, &size, nullptr, 0) == 0) { + return static_cast<double>(freq); + } + return 1.0; +} + +#else + +// Helper function for reading a long from a file. Returns true if successful +// and the memory location pointed to by value is set to the value read. +static bool ReadLongFromFile(const char *file, long *value) { + bool ret = false; + int fd = open(file, O_RDONLY); + if (fd != -1) { + char line[1024]; + char *err; + memset(line, '\0', sizeof(line)); + int len = read(fd, line, sizeof(line) - 1); + if (len <= 0) { + ret = false; + } else { + const long temp_value = strtol(line, &err, 10); + if (line[0] != '\0' && (*err == '\n' || *err == '\0')) { + *value = temp_value; + ret = true; + } + } + close(fd); + } + return ret; +} + +#if defined(ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY) + +// Reads a monotonic time source and returns a value in +// nanoseconds. The returned value uses an arbitrary epoch, not the +// Unix epoch. +static int64_t ReadMonotonicClockNanos() { + struct timespec t; +#ifdef CLOCK_MONOTONIC_RAW + int rc = clock_gettime(CLOCK_MONOTONIC_RAW, &t); +#else + int rc = clock_gettime(CLOCK_MONOTONIC, &t); +#endif + if (rc != 0) { + perror("clock_gettime() failed"); + abort(); + } + return int64_t{t.tv_sec} * 1000000000 + t.tv_nsec; +} + +class UnscaledCycleClockWrapperForInitializeFrequency { + public: + static int64_t Now() { return base_internal::UnscaledCycleClock::Now(); } +}; + +struct TimeTscPair { + int64_t time; // From ReadMonotonicClockNanos(). + int64_t tsc; // From UnscaledCycleClock::Now(). +}; + +// Returns a pair of values (monotonic kernel time, TSC ticks) that +// approximately correspond to each other. This is accomplished by +// doing several reads and picking the reading with the lowest +// latency. This approach is used to minimize the probability that +// our thread was preempted between clock reads. +static TimeTscPair GetTimeTscPair() { + int64_t best_latency = std::numeric_limits<int64_t>::max(); + TimeTscPair best; + for (int i = 0; i < 10; ++i) { + int64_t t0 = ReadMonotonicClockNanos(); + int64_t tsc = UnscaledCycleClockWrapperForInitializeFrequency::Now(); + int64_t t1 = ReadMonotonicClockNanos(); + int64_t latency = t1 - t0; + if (latency < best_latency) { + best_latency = latency; + best.time = t0; + best.tsc = tsc; + } + } + return best; +} + +// Measures and returns the TSC frequency by taking a pair of +// measurements approximately `sleep_nanoseconds` apart. +static double MeasureTscFrequencyWithSleep(int sleep_nanoseconds) { + auto t0 = GetTimeTscPair(); + struct timespec ts; + ts.tv_sec = 0; + ts.tv_nsec = sleep_nanoseconds; + while (nanosleep(&ts, &ts) != 0 && errno == EINTR) {} + auto t1 = GetTimeTscPair(); + double elapsed_ticks = t1.tsc - t0.tsc; + double elapsed_time = (t1.time - t0.time) * 1e-9; + return elapsed_ticks / elapsed_time; +} + +// Measures and returns the TSC frequency by calling +// MeasureTscFrequencyWithSleep(), doubling the sleep interval until the +// frequency measurement stabilizes. +static double MeasureTscFrequency() { + double last_measurement = -1.0; + int sleep_nanoseconds = 1000000; // 1 millisecond. + for (int i = 0; i < 8; ++i) { + double measurement = MeasureTscFrequencyWithSleep(sleep_nanoseconds); + if (measurement * 0.99 < last_measurement && + last_measurement < measurement * 1.01) { + // Use the current measurement if it is within 1% of the + // previous measurement. + return measurement; + } + last_measurement = measurement; + sleep_nanoseconds *= 2; + } + return last_measurement; +} + +#endif // ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY + +static double GetNominalCPUFrequency() { + long freq = 0; + + // Google's production kernel has a patch to export the TSC + // frequency through sysfs. If the kernel is exporting the TSC + // frequency use that. There are issues where cpuinfo_max_freq + // cannot be relied on because the BIOS may be exporting an invalid + // p-state (on x86) or p-states may be used to put the processor in + // a new mode (turbo mode). Essentially, those frequencies cannot + // always be relied upon. The same reasons apply to /proc/cpuinfo as + // well. + if (ReadLongFromFile("/sys/devices/system/cpu/cpu0/tsc_freq_khz", &freq)) { + return freq * 1e3; // Value is kHz. + } + +#if defined(ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY) + // On these platforms, the TSC frequency is the nominal CPU + // frequency. But without having the kernel export it directly + // though /sys/devices/system/cpu/cpu0/tsc_freq_khz, there is no + // other way to reliably get the TSC frequency, so we have to + // measure it ourselves. Some CPUs abuse cpuinfo_max_freq by + // exporting "fake" frequencies for implementing new features. For + // example, Intel's turbo mode is enabled by exposing a p-state + // value with a higher frequency than that of the real TSC + // rate. Because of this, we prefer to measure the TSC rate + // ourselves on i386 and x86-64. + return MeasureTscFrequency(); +#else + + // If CPU scaling is in effect, we want to use the *maximum* + // frequency, not whatever CPU speed some random processor happens + // to be using now. + if (ReadLongFromFile("/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq", + &freq)) { + return freq * 1e3; // Value is kHz. + } + + return 1.0; +#endif // !ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY +} + +#endif + +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_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_nominal_cpu_frequency_once, + []() { nominal_cpu_frequency = GetNominalCPUFrequency(); }); + return nominal_cpu_frequency; +} + +#if defined(_WIN32) + +pid_t GetTID() { + return pid_t{GetCurrentThreadId()}; +} + +#elif defined(__linux__) + +#ifndef SYS_gettid +#define SYS_gettid __NR_gettid +#endif + +pid_t GetTID() { + return syscall(SYS_gettid); +} + +#elif defined(__akaros__) + +pid_t GetTID() { + // Akaros has a concept of "vcore context", which is the state the program + // is forced into when we need to make a user-level scheduling decision, or + // run a signal handler. This is analogous to the interrupt context that a + // CPU might enter if it encounters some kind of exception. + // + // There is no current thread context in vcore context, but we need to give + // a reasonable answer if asked for a thread ID (e.g., in a signal handler). + // Thread 0 always exists, so if we are in vcore context, we return that. + // + // Otherwise, we know (since we are using pthreads) that the uthread struct + // current_uthread is pointing to is the first element of a + // struct pthread_tcb, so we extract and return the thread ID from that. + // + // TODO(dcross): Akaros anticipates moving the thread ID to the uthread + // structure at some point. We should modify this code to remove the cast + // when that happens. + if (in_vcore_context()) + return 0; + return reinterpret_cast<struct pthread_tcb *>(current_uthread)->id; +} + +#elif defined(__myriad2__) + +pid_t GetTID() { + uint32_t tid; + rtems_task_ident(RTEMS_SELF, 0, &tid); + return tid; +} + +#else + +// Fallback implementation of GetTID using pthread_getspecific. +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(). +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. +static void FreeTID(void *v) { + intptr_t tid = reinterpret_cast<intptr_t>(v); + int word = tid / kBitsPerWord; + uint32_t mask = ~(1u << (tid % kBitsPerWord)); + absl::base_internal::SpinLockHolder lock(&tid_lock); + assert(0 <= word && static_cast<size_t>(word) < tid_array->size()); + (*tid_array)[word] &= mask; +} + +static void InitGetTID() { + if (pthread_key_create(&tid_key, FreeTID) != 0) { + // The logging system calls GetTID() so it can't be used here. + perror("pthread_key_create failed"); + abort(); + } + + // Initialize tid_array. + absl::base_internal::SpinLockHolder lock(&tid_lock); + tid_array = new std::vector<uint32_t>(1); + (*tid_array)[0] = 1; // ID 0 is never-allocated. +} + +// Return a per-thread small integer ID from pthread's thread-specific data. +pid_t GetTID() { + absl::call_once(tid_once, InitGetTID); + + intptr_t tid = reinterpret_cast<intptr_t>(pthread_getspecific(tid_key)); + if (tid != 0) { + return tid; + } + + int bit; // tid_array[word] = 1u << bit; + size_t word; + { + // Search for the first unused ID. + absl::base_internal::SpinLockHolder lock(&tid_lock); + // First search for a word in the array that is not all ones. + word = 0; + while (word < tid_array->size() && ~(*tid_array)[word] == 0) { + ++word; + } + if (word == tid_array->size()) { + tid_array->push_back(0); // No space left, add kBitsPerWord more IDs. + } + // Search for a zero bit in the word. + bit = 0; + while (bit < kBitsPerWord && (((*tid_array)[word] >> bit) & 1) != 0) { + ++bit; + } + tid = (word * kBitsPerWord) + bit; + (*tid_array)[word] |= 1u << bit; // Mark the TID as allocated. + } + + if (pthread_setspecific(tid_key, reinterpret_cast<void *>(tid)) != 0) { + perror("pthread_setspecific failed"); + abort(); + } + + return static_cast<pid_t>(tid); +} + +#endif + +} // namespace base_internal +ABSL_NAMESPACE_END +} // namespace absl |