Get CPU percent usage on macOS

Question

I'm a beginner in Objective-C, and I decided to try to write some simple application, so I'm trying to make an app which would measure CPU usage and such. Is there a simple way to get information such as the CPU percent usage using Objective-C in a Cocoa application?

I have found this question Determine Process Info Programmatically in Darwin/OSX which is similar, but not exactly the same. Mainly, I want the CPU percent usage of the whole system, not just my process, and I would actually prefer an Objective-C solution whereas in that question the poster wanted something else.

Answer 1

Here is the way i did it:

*.h file:

#include <sys/sysctl.h>
#include <sys/types.h>
#include <mach/mach.h>
#include <mach/processor_info.h>
#include <mach/mach_host.h>

ivars:

processor_info_array_t cpuInfo, prevCpuInfo;
mach_msg_type_number_t numCpuInfo, numPrevCpuInfo;
unsigned numCPUs;
NSTimer *updateTimer;
NSLock *CPUUsageLock;

*.m file

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{    
    int mib[2U] = { CTL_HW, HW_NCPU };
    size_t sizeOfNumCPUs = sizeof(numCPUs);
    int status = sysctl(mib, 2U, &numCPUs, &sizeOfNumCPUs, NULL, 0U);
    if(status)
        numCPUs = 1;

    CPUUsageLock = [[NSLock alloc] init];

    updateTimer = [[NSTimer scheduledTimerWithTimeInterval:3
                                                    target:self
                                                  selector:@selector(updateInfo:)
                                                  userInfo:nil
                                                   repeats:YES] retain];    
}

- (void)updateInfo:(NSTimer *)timer
{
    natural_t numCPUsU = 0U;
    kern_return_t err = host_processor_info(mach_host_self(), PROCESSOR_CPU_LOAD_INFO, &numCPUsU, &cpuInfo, &numCpuInfo);
    if(err == KERN_SUCCESS) {
        [CPUUsageLock lock];

        for(unsigned i = 0U; i < numCPUs; ++i) {
            float inUse, total;
            if(prevCpuInfo) {
                inUse = (
                         (cpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_USER]   - prevCpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_USER])
                         + (cpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_SYSTEM] - prevCpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_SYSTEM])
                         + (cpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_NICE]   - prevCpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_NICE])
                         );
                total = inUse + (cpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_IDLE] - prevCpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_IDLE]);
            } else {
                inUse = cpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_USER] + cpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_SYSTEM] + cpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_NICE];
                total = inUse + cpuInfo[(CPU_STATE_MAX * i) + CPU_STATE_IDLE];
            }

            NSLog(@"Core: %u Usage: %f",i,inUse / total);
        }
        [CPUUsageLock unlock];

        if(prevCpuInfo) {
            size_t prevCpuInfoSize = sizeof(integer_t) * numPrevCpuInfo;
            vm_deallocate(mach_task_self(), (vm_address_t)prevCpuInfo, prevCpuInfoSize);
        }

        prevCpuInfo = cpuInfo;
        numPrevCpuInfo = numCpuInfo;

        cpuInfo = NULL;
        numCpuInfo = 0U;
    } else {
        NSLog(@"Error!");
        [NSApp terminate:nil];
    }
}