Monitor memory usage in an iphone app?

Question

Is it possible to monitor the amount of memory your app is consuming?

Answer 1

Actually, it's probably more important you know how much memory is free, rather than how much your app is using. Here's some code to do that:

#import <mach/mach.h>
#import <mach/mach_host.h>

+(natural_t) get_free_memory {
    mach_port_t host_port;
    mach_msg_type_number_t host_size;
    vm_size_t pagesize;
    host_port = mach_host_self();
    host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
    host_page_size(host_port, &pagesize);
    vm_statistics_data_t vm_stat;

    if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS) {
        NSLog(@"Failed to fetch vm statistics");
        return 0;
    }

    /* Stats in bytes */
    natural_t mem_free = vm_stat.free_count * pagesize;
    return mem_free;
}

Answer 2

Yes. In Xcode, open your project and choose Run > Run with Performance Tool > Allocations. This will start an application called Instruments, which can be used to analyze your app. In that specific case it will record all object allocations which gives you a good overview of your memory footprint. You can use this with both, the iOS Simulator and an actual device. You should prefer to analyze the app while running on an iOS device to get optimal results.

Instruments can do a lot more to help you optimize your apps, so you should give the Instruments User Guide a closer look.