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why did my app just used about 36MB memory but i still receive low memory warning?

Answer 1

+1 A:

Sounds like a memory leak to me, you might want to check in that direction.

Razor 2010-08-09 09:53:36

Answer 2

+1 A:

Are you trying to load huge amount of data in a very short time? This is specially the case when trying to run an image view animation sequence. I got a crash when the memory was less than 20MB. After investigation I found that my image sequence contained very big images and the reason of crash was not total memory load. The reason was memory bandwidth.

taskinoor 2010-08-09 09:56:48

"Memory bandwidth" does not cause a crash.

tc. 2010-08-09 12:49:27

really? try to load 20MB of data from disk to RAM and from RAM to VRAM and see what happens.

taskinoor 2010-08-09 14:09:04

At one time the most data i load may be tens of *.png . About hundreds KB.

ben 2010-08-10 00:57:19

then this might not be ur problem. i got a crash on a 2g device while trying to load about 15 320 x 480 png images. but after preloading, the problem was resolved.

taskinoor 2010-08-10 05:41:30

@taskinoor - What's causing the crash in your case is not memory bandwidth, but a spike in memory usage. If your application ever crosses the threshold for being killed (30 MB of total usage on earlier devices), it will be terminated.

Brad Larson 2010-08-10 12:54:58

usually, memory warning also comes in when you run the other third party big memory resourced based app in the iOS 4.0.

Yoon Lee 2010-09-16 12:33:39

Answer 3

+1 A:

If you're on an older model like a 2g or 3g, 36 megs is probably more ram than you've got to play with. I usually start getting warnings around 25mb.

Dan Ray 2010-08-09 12:19:17

Answer 4

+1 A:

You get memory warnings when phone memory is low. "Level 1" memory warnings are pretty normal. If your app is crashing, then it's probably because you're not handling the memory warning properly rather than because you're using too much memory. There are two fixes:

Ignore the memory warning (don't super-call in didReceiveMemoryWarning)
Fix your code

tc. 2010-08-09 12:49:04

Answer 5

+1 A:

Seems to be a memory leak. To find it, use not only "Leaks" Instrument. "Allocations" also can help you. Use it actively, mark heaps, compare memory usage and examine "still alive" objects (especially objects of your own classes).

Sometimes memory leaks can't be automatically detected (with "Leaks" Instrument). For example, imagine that you have some UIImageView. This image view should be created, when user touches "Create" button, and destroyed, when he touches "Destroy" button. You can implement this behavior like in code below:

- (IBAction)bCreateTouchUpInside:(id)sender {
    ivSomeImageView = [[UIImageView alloc] initWithImage:iSomeImage];
    [self.view addSubview:ivSomeImageView];
    bCreate.enabled = NO;   bDestroy.enabled = YES;
}

- (IBAction)bDestroyTouchUpInside:(id)sender {
    [ivSomeImageView release];
    bCreate.enabled = YES;   bDestroy.enabled = NO;
}

And there will be a memory leak: two-times retained (creation + addSubview), one-time released (release). To solve the problem, you should add [ivSomeImageView removeFromSuperview]; before direct release message. But this leak won't be detected by "Leaks" Instrument, cause there is a correct pointer to your image view (parent view stores pointers to it's subviews). And the only chance to detect this leak for you is to press "Create" for numerous times and to see that memory usage increases each time.

kpower 2010-08-10 08:36:51

Answer 6

+3 A:

I think it's telling you exactly what the problem is: you're using too much memory. If the OS tells you this and you do nothing about it then it may (indeed, does) eject your program from memory.

You don't post any code so it's not clear whether you have a memory leak or are just using too much memory. Try using the static analyser (in the build menu of Xcode) and the Leaks part of Instruments to check for leaks. If it doesn't find any then you may just have to optimise your app to use less memory.

I'm not sure where you found that 36Mb is okay. On first gen devices you'll get kicked out of memory much above 20Mb. I don't think there's any absolute number documented, so you need to do two things: test on real devices and release as much memory as possible when it tells you that you're using too much.

Stephen Darlington 2010-08-10 09:36:25

yeah，i test it with my ipad,i think the problem most likely that i use too much memory,i can run my app at the 36-40MB memory used for 20 min at least.i think it's regular

ben 2010-08-10 09:52:19

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why did my app just used about 36MB memory but i still receive low memory warning?

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