cpuinfo

cpuinfo is a cross-platform C/C++ library designed to detect essential host CPU information required for performance optimization. It provides thread-safe access to CPU details with no memory allocation after initialization and no exceptions thrown.

Key Capabilities:

• Instruction Set Detection: Supports up to AVX512 (x86) and ARMv8.3 extensions.
• SoC & Core Info: Detects processor names, vendors, and microarchitectures (including support for heterogeneous cores like big.LITTLE).
• Cache Information: Provides details on cache type, size, line size, associativity, and topology.
• Topology Information: Maps relationships between logical processors, cores, and processor packages.

Supported Platforms:

• Linux: x86, x86-64, 32-bit ARM, ARM64
• Windows: x86, x86-64, arm64
• macOS: x86, x86-64, ARM64 (Apple silicon)
• Android: x86, x86_64, armeabi, armeabiv7-a, arm64-v8a
• iOS: x86, x86-64, ARMv7, ARM64
• FreeBSD: x86-64

To use clog in a module, you must first define the logging functions for that module using the CLOG_DEFINE_LOG_* macros. This allows you to specify a prefix, a module name, and a log level. Once defined, you can use the generated functions (which follow the pattern prefix_log_<level>) to log messages using printf-style formatting.

Commonly used macros for definition:

• CLOG_DEFINE_LOG_DEBUG(prefix, name, level)
• CLOG_DEFINE_LOG_INFO(prefix, name, level)
• CLOG_DEFINE_LOG_WARNING(prefix, name, level)
• CLOG_DEFINE_LOG_ERROR(prefix, name, level)

#include <clog.h>

#ifndef MYMODULE_LOG_LEVEL
    #define MYMODULE_LOG_LEVEL CLOG_DEBUG
#endif

// Define loggers for the module
CLOG_DEFINE_LOG_DEBUG(mymodule_, "My Module", MYMODULE_LOG_LEVEL);
CLOG_DEFINE_LOG_INFO(mymodule_, "My Module", MYMODULE_LOG_LEVEL);
CLOG_DEFINE_LOG_WARNING(mymodule_, "My Module", MYMODULE_LOG_LEVEL);
CLOG_DEFINE_LOG_ERROR(mymodule_, "My Module", MYMODULE_LOG_LEVEL);

void some_function(int status, uint32_t expected_zero, void* usually_non_null, float a) {
    if (status != 0) {
        // Uses the error logger
        mymodule_log_error(
            "something really bad happened: "
            "operation failed with status %d", status);
    }

    if (expected_zero != 0) {
        // Uses the warning logger
        mymodule_log_warning(
            "something suspicious happened (var = %"PRIu32"), "
            "fall back to generic implementation", expected_zero);
    }

    if (usually_non_null == NULL) {
        // Uses the info logger
        mymodule_log_info(
            "something unusual, but common, happened: "
            "enabling work-around");
    }

    // Uses the debug logger
    mymodule_log_debug("computed a = %.7f", a);
}

The library provides several C functions to query CPU capabilities and topology. Note that most operations require calling cpuinfo_initialize() first.

Log Processor Name

cpuinfo_initialize();
printf("Running on %s CPU\n", cpuinfo_get_package(0)->name);

Check Instruction Set Support (ARM NEON or x86 AVX)

cpuinfo_initialize();
if (cpuinfo_has_arm_neon()) {
    neon_implementation(arguments);
}

if (cpuinfo_has_x86_avx()) {
    avx_implementation(arguments);
}

Identify Microarchitecture

Use cpuinfo_get_current_core()->uarch to check for specific core types (e.g., Cortex-A53).

cpuinfo_initialize();
switch (cpuinfo_get_current_core()->uarch) {
    case cpuinfo_uarch_cortex_a53:
        cortex_a53_implementation(arguments);
        break;
    default:
        generic_implementation(arguments);
        break;
}

Access Cache Information

Get the size of the L1 data cache on the fastest core:

cpuinfo_initialize();
const size_t l1_size = cpuinfo_get_processor(0)->cache.l1d->size;

Pin Thread to Cores Sharing L2 Cache (Linux/Android)

cpuinfo_initialize();
cpu_set_t cpu_set;
CPU_ZERO(&cpu_set);
const struct cpuinfo_cache* current_l2 = cpuinfo_get_current_processor()->cache.l2;
for (uint32_t i = 0; i < current_l2->processor_count; i++) {
    CPU_SET(cpuinfo_get_processor(current_l2->processor_start + i)->linux_id, &cpu_set);
}
pthread_setaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpu_set);