gpu_usage.m

#include "gpu_usage.h"
#ifdef __APPLE__

#include <CoreFoundation/CoreFoundation.h>
#include <Cocoa/Cocoa.h>
#include <IOKit/IOKitLib.h>
#include <IOKit/graphics/IOGraphicsLib.h>

float getGPUCoreUsage(int gpu_number) {

   static ssize_t gpuUsage=0;
   int i = 0;
   CFMutableDictionaryRef dict = IOServiceMatching(kIOAcceleratorClassName);
   io_iterator_t it;

   if (IOServiceGetMatchingServices(kIOMasterPortDefault,dict,
                                    &it) == kIOReturnSuccess) {
      io_registry_entry_t entry;
      while ((entry = IOIteratorNext(it))) {
         CFMutableDictionaryRef serviceDictionary;
         if (IORegistryEntryCreateCFProperties(entry,
                                               &serviceDictionary,
                                               kCFAllocatorDefault,
                                               kNilOptions) != kIOReturnSuccess) {
            IOObjectRelease(entry);
            IOObjectRelease(it);
            return 0;
         }

         CFMutableDictionaryRef properties = (CFMutableDictionaryRef) CFDictionaryGetValue( serviceDictionary, CFSTR("PerformanceStatistics") );
         if (properties) {
            const void* gpuCoreUtilization = CFDictionaryGetValue(properties, CFSTR("GPU Core Utilization"));
            if (gpuCoreUtilization) {
               CFNumberGetValue( (CFNumberRef) gpuCoreUtilization, kCFNumberSInt64Type, &gpuUsage);
            }
         }

         CFRelease(serviceDictionary);
         IOObjectRelease(entry);
         if (i == gpu_number) {
            IOObjectRelease(it);
            return gpuUsage/10000000;
         }
         i++;
      }
      IOObjectRelease(it);
   }
   return 0;
}
#endif