确定 iOS 设备上的可用 RAM 量 [英] Determining the available amount of RAM on an iOS device

问题描述

您可能已经看到许多系统信息"应用程序，它们显示剩余电池寿命，甚至内存等系统信息.

You've likely seen the many "System Info" apps out there which display things like remaining battery life, and even system info like memory, etc.

以类似的方式，是否有任何方法可以从我的应用中检索当前可用 RAM 量，以便我可以更好地决定何时最好转储或保留某些视图以避免内存警告?

In a similar manner, is there any way to retrieve the current amount of available RAM from my app so that I can make better decisions on when it's best to dump or keep certain views to avoid memory warnings?

推荐答案

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

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);
}

请注意，此调用不考虑 GPU 正在使用的内存.如果您看到的大小小于预期的系统内存.很可能分配了图形内存.

Please note that this call does not account for memory that is being used by the gpu. If you are seeing a size that is smaller than expected system ram. It is more than likely allocated graphics memory.

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