[xcode] iOS iphone memory check

iPhone: Determining Available Memory

The iPhone has limited memory, and even simple applications can easily trigger a low memory warning. If you've implemented caching for performance reasons, you'll often find yourself balancing memory consumption against user experience.

Measuring the current available RAM allows one to make pre-emptive decisions about memory utilization before a low memory warning is triggered, possibly avoiding overly broad cache evictions when a memory warning is triggered.

I've seen this question come up a number of times, so here's a brief code snippet demonstrating how to determine available memory from the Mach VM statistics.

#import <mach/mach.h>

#import <mach/mach_host.h>

 

static void print_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");

 

    /* Stats in bytes */ 

    natural_t mem_used = (vm_stat.active_count +

                          vm_stat.inactive_count +

                          vm_stat.wire_count) * pagesize;

    natural_t mem_free = vm_stat.free_count * pagesize;

    natural_t mem_total = mem_used + mem_free;

    NSLog(@"used: %u free: %u total: %u", mem_used, mem_free, mem_total);

}

함수를 호출하면 호출할 당시의  사용된메모리 남은메모리 총메모리가 출력됩니다 

(단위:바이트)

이를 응용해서 어플 실행하자마자 메모리와 리소스 로드후 메모리를 비교하면 현 어플의 실 사용 메모리도 알수 있습니다.

출처

http://landonf.bikemonkey.org/code/iphone/Determining_Available_Memory.20081203.html
http://javawoo.tistory.com/10