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Answer 1

+1 A:

There is no defined maximum amount of memory that an iPhone app can use. Whether your app will be terminated due to lack of memory depends on whatever algorithms the OS is using and what other apps happen to be using memory at the same time (safari, mail, etc.).

Mike Weller 2010-05-09 18:46:12

The OS will kill off safari, mail, etc threads as needed if you are running low on memory. You can see this in the console logs as you get low on memory.

progrmr 2010-05-09 21:36:22

Does this mean that Ben Gottlieb's answer is wrong?

hgpc 2010-05-10 05:00:10

@hgpc, his way to find how to find availiable *system memory', since system will free more for you if you keep allocating, it's not a definate number and if you allocate too much, your process get killed. No iphone application should use more overf 30MB of memory under my understanding.

overboming 2010-05-10 06:16:44

This is for information only; the system will try to clear memory for you, so this number should not be taken as hard-and-fast. I mainly use it as a way to see how much memory I'M using; watching the number fluctuate, if it starts to drop reliably, it probably indicates a memory leak, or at least a resource hog.

Ben Gottlieb 2010-05-10 11:28:14

Answer 2

+2 A:

This function will return the available memory in bytes:

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

natural_t  freeMemory(void) {
    mach_port_t           host_port = mach_host_self();
    mach_msg_type_number_t   host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
    vm_size_t               pagesize;
    vm_statistics_data_t     vm_stat;

    host_page_size(host_port, &pagesize);

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

    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;

    return mem_free;
}

Ben Gottlieb 2010-05-09 18:56:34

Thanks Ben. Just to confirm, does your solution use any private APIs? Which libraries should I import to use it?

hgpc 2010-05-10 05:01:21

Nope, no private APIs.

Ben Gottlieb 2010-05-10 11:26:39

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Available memory for iPhone OS app

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