is it possible, that when the iPad application is forcibly closed/killed by the iOS becuase of 'out of memory situation', the memory the application allocated is not 100% released? I think that the memory allocated directly by the client is released - there is even HW support for this, but we were observing that if the application is closed/killed by iOS and consequently started again less and less memory is available, until the iPad must be restarted. We think that some memory are allocated e.g. by background running daemons, which do some job on behalf of application and if the inter-process communication is not successfully finished, used memory on the daemon side might not be released properly...
Is something like this possible?
BR
STeN
If you alloc memory it will stay in the heap until you release it, even if the app that did the alloc is long gone. Like you have seen restarting the device will clear the heap.
You should always manage memory events, there is a method for this.
- (void)didReceiveMemoryWarning;
typically you would release everything you can, especially if its a level 2, as if you don't your app is going to close anyway.
However, When your app exits it should be calling dealloc anyway! so you may have a general leak.
I'm fairly certain that the method:
- (void)applicationWillTerminate:(UIApplication *)application;
will run even if the app is crashing. This would be a good time to ensure that everything is released, if it is not getting caught by the memoryWarning.
Related
I have a Dictionary of SKTextures that caches recently loaded textures (70 or so). I'm releasing them when a memory warning is received, like this:
let keys = textures.keys.array
for key in keys {
textures[key] = nil
}
This works great, and I can see in the Xcode debugger that the memory is actually being freed.
When I try to release them on applicationDidEnterBackground(), however, it doesn't look like it fully works. The memory usage drops by a small inconsistent amount (5-20 MB), but the rest of it doesn't get freed until the app is resumed.
Is this a quirk with the debugger and the memory is being freed? Or does the garbage collector not have enough time to clean up before the app is suspended? Or am I doing this all wrong?
Update: I'm pretty sure it's related to SpriteKit automatically pausing the SKView when entering the background. This is easily reproducible by pausing the view manually just before releasing the textures. Then the memory won't be freed even when the memory warning is received.
Is this a quirk with the debugger and the memory is being freed
I would describe it a quirk of how memory management works. There's a virtual memory management system. The memory is being freed but that doesn't mean that it is emptied / reclaimed, if you see what I mean. What you've done is to say that this memory is free, but the system won't take it unless it needs it.
The way to test is to write another app that deliberately gobbles memory, and run it while your app is in the background. Instruments will work even when you are suspended, and will show that in fact your memory usage goes down.
How can I make sure that reason of crashes is lack of memory?
Is there anything specific in crash log?
Maybe I have to use some tools or libraries?
UPDATE: my app uses lot of memory and receives memory warnings. It's very difficult to reduce memory usage. It crashes because of memory warnings time to time. But I want to make sure that it doesn't crash because of other reasons.
So how can I check the reason of app crash (it receives lots of memory warnings every time)
UPDATE2: Application has lots of 3D graphics and complex UI that takes lots of memory for textures. Customer doesn't want to make any kind of "loading..." pauses. If I unload invisible textures in background I can't get smooth animations.
So I just need to detect is there any crash reasons except memory.
At least you could implement the method
- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application
in your app delegate, and put a log to see if this indeed you are going through it before crashing.
Product -> Profile -> leak is a possible method to check memory leak. Allocations will show the total memory being used, and leaks will show leaks due to not releasing.
how-to-debug-memory-leaks-with-xcode-and-instruments-tutorial
that is a useful tutorial
You can use Apple's Instruments Tool to profile various things such as memory usage. This tool is bundled together with Xcode.
I've kind of a weird issue with my iOS app.
after a while my app goes low in memory so memory warning, everything seems to be fine, but when I check the memory usage I noticed that all the calls to viewDidUnload didn't free up lot of memory, so after a few click in my app, it goes again in memory warning, everything seems to be fine again, but not a lot a memory have been released, so it goes again in memory warning faster, and then it crash (after the third memory warning most of the time). this crash is random : app freeze, app leaves, my debugger says app paused, but no bad access or sigbort, no zombies.
my guess is that memory warning can't free up enough memory has it should.
(I checked all my viewDidUnload and make nil every objects that are allocated in viewDidLoad)
Any help will be usefull !
thanks a lot.
So I managed to work with my issue.
I wrote "-(void) dealloc" methode in all my controllers and check if I enter in it as I should. (on pop controller, dissmiss etc..)
Every time it didn't, I do step by step in the controller to see what was retaining my controller from beeing dealloc.
most of the time it was some property that was not in "unsafe_unretained"
delegate that was in "ASSIGN" (and should not be in assign but in unsafe_unretained)
(heritage from non-ARC project...)
I also had some strange controller with XIB that was not deallocated even if empty.
I rebuild new one step by step with copy/paste and finaly with exactly the same code, the new controller was released, with no visible difference between then !!! gnneee
at least I know how to debug that kind issues now...
I don't think there's any way to give a specific answer without more data so the best I can do is suggest that you stop guessing what might be happening with your app and learn how to measure what is actually going on. Run your app under Instruments and you'll be able to check for leaks and also actually see what classes are responsible for the most of your application's memory footprint.
You should make sure you know how to use both the Leaks instrument to identify leaked object but also the Allocations instrument to identify orphaned (but not leaked) sets of objects which should have been released or just cases where your app is not responding to memory warnings as you expected.
https://developer.apple.com/library/ios/#documentation/developertools/conceptual/InstrumentsUserGuide/AboutTracing/AboutTracing.html might be a good place to start and there are a number of tutorials available as well; http://www.raywenderlich.com/2696/how-to-debug-memory-leaks-with-xcode-and-instruments-tutorial and http://www.friday.com/bbum/2010/10/17/when-is-a-leak-not-a-leak-using-heapshot-analysis-to-find-undesirable-memory-growth/ are among the first results I saw.
Vassily,
First, if you aren't yourself releasing extra memory, the the -didReceiveMemory warning does you no good and the OS will keep asking for memory until you are killed. This sounds like it is your problem.
Second, if that isn't the problem then you are probably getting terminated due to the size of your resident memory partitions. Make sure you look at your VM allocation in Instruments. I expect the MALLOC_TINY or MALLOC_SMALL both have greater than 5 MB resident and dirty footprints. Due to the nature of small allocations these VM regions will never shrink. The only option you really have is to not create a lot of small items in the first place. This is really only something you can address by changing you code's algorithms to use less memory.
Andrew
Writing a program for the iphone. Realized that I forgot to release an object, but there was really no indication that the object was not released everything just worked.
What is the best way to track something like this down? Is there a way to see what objects still exist in memory when the program exits out?
Take a look at the Leaks tool in Instruments.
Strictly speaking, when the program exits, it doesn’t matter what you’ve left in memory: the system frees everything that your application allocated throughout its lifetime. Since iOS 4, though, apps usually just get frozen in the background and don’t exit until the system kills them to free up memory. To avoid that—and to reduce your app’s memory footprint, which is important while it’s running—you should, as highlycaffeinated and Daniel suggested, use Instruments’s Leaks tool to check for objects that aren’t getting deallocated properly.
When the app exits, anything in memory is destroyed by the system (not deallocated-- but just outright destroyed when the address space is given back to the system).
While others have suggested using the Leaks tool to find leaks in your app, Leaks won't find many many kinds of memory accretion. If an object is allocated, shoved in a cache somewhere, then the key to that object in the cache is lost, the object is effectively leaked (can never be used again) but won't be find by Leaks because it is still connected to your viable object graph.
A better bet is to use Heapshot analysis to see how your app's object graph grows over time. I wrote up a tutorial on using Heapshot analysis that you might find useful.
If you want to grab a snapshot just before your app exits, then put a sleep(1000); into your code in either an application termination handler or somewhere else that is executed just before the app exits.
Just remember to remove it before shipping a production build. :)
Once an application quits - you don't have access to that. But Instruments (an XCode tool) can look for memory leaks.
Nothing exists in memory when pprogram exits. But you can start with analyzing your code (Product -> Analyze) and running it with (Product -> Profile) Allocations or Leaks in Instruments to find memory management issues.
I am running an ipad application compiled for release and am seing memory warnings once in a while.
When I run the app on the device and connect Instruments, I see that the app never passes 40MB of real memory, but the warnings are still occurring.
What might be causing this? How can I better track down the reason?
40 MB of real memory is a lot, for an iPad. Even if it was not, the system will deliver the low-memory warning to you from time to time anyway, without your application being the main culprit. Tracking down precise memory usage in your application is sometimes hard, I’d suggest to spend some time with the Object Allocation instrument while working with the app. If you are not getting killed and you are sure that you do not leak the memory, you can also simply ignore the warnings.
40MB is high for the iPad considering it only has 256MB to start with. There could be other applications holding on to memory which will be killed off as more memory is needed. Just make sure you aren't leaking anything. Also use NSAutoReleasePools where applicable to reduce peak memory usage in memory intensive loops.