I have this code in my app:
var newImage = // ...
if (imageView.Image != null && imageView.Image != newImage)
imageView.Image.Dispose ();
imageView.Image = newImage;
I have three related questions:
Does it immediately release the memory occupied by the previous imageView.Image?
If it does, is there a cleaner solution?
Does this have anything to do with NSAutoreleasePool?
Does it immediately release the memory occupied by the previous imageView.Image?
Not immediately but it should be much faster than waiting for the Garbage Collector.
Calling Dispose will drop the managed reference to the native UIImage. If nothing else (natively) has a reference to the UIImage (RetainCount == 0) then it will be freed (ObjC reference counting).
In your code imageView still has a reference to it until its Image property is set to newImage - which is why I answered not immediately.
If it does, is there a cleaner solution?
Not really. Letting the GC do it's work is cleaner looking - but image can be very big and are worth freeing asap.
Also it's not really worth (and would not be cleaner anyway) adding a local variable to make sure (if no other native reference exists) the image will be freed immediately - it will happen on the next line.
Does this have anything to do with NSAutoreleasePool?
Anything ? well it's memory related in both cases.
Creating images will use (cache) the current NSAutoreleasePool and will, eventually, be drained. If you process a lot of stuff (e.g. a loop) then it's often worth having your own, short-lived, pool to ensure a faster drain.
Some API (well know to require a lot of memory) are decorated with an attribute that will automatically add (btouch) an NSAutoreleasePool - but it's not easy to find out which.
In doubt you better use Apple Instruments to measure...
Related
My app crashes on devices with 0.5GB memory. However, profiling memory usage in Xcode - it rarely goes above 140MB. I've used instruments to check leaks and there are none that are significant.
However, when I run my app, the memory used by 'Other Processes' is always very high. This is the resting state after launching:
I added a 1 second delay in each cycle of a loop in my code, and discovered that on each loop, the 'other processes' increases memory usage by about 3MB per object, until on 0.5GB devices, it runs out and crashes.
This question suggests that these are other apps using that memory, but I have closed every other app and the usage directly correlates with my looping code.
What could be using memory in other processes, that is actually running in my app? And why is my 'Other Processes' using up so much memory?
To give an idea of what I'm doing, I'm pulling data from Parse, then looping through each of the objects returned and creating an SKNode subclass object from the data. I add this node to an array, (for reference) and to the scene. Here's the code I'm doing on the main thread with the delay added. NB the line:
self drawRelationships:[_batches objectAtIndex:_index] forMini:_playerMini];
Is a BFTask and so asynchronous. And I'm dividing the array into smaller batches so I can see incremental memory usage, as each batch is drawn. If I try to draw the whole lot at once, OOM occurs immediately...
- (void)drawNewRelationships
{
_batches = [NSMutableArray array];
_index = 0;
[_playerMini fetchInBackgroundWithBlock:^(PFObject *object, NSError *error) {
[ParseQuery getNewRelationshipsForMini:_playerMini current:_miniRows.relationshipIds withBlock:^(NSMutableArray *newRelationships) {
_batches = [self batchArrays:3 fromArray:newRelationships];
_index = 0;
[self drawBatches];
}];
}];
}
- (void)drawBatches
{
if ([_batches objectAtIndex:_index]) {
[self drawRelationships:[_batches objectAtIndex:_index] forMini:_playerMini];
_index++;
if (_index < [_batches count]) {
[self performSelector:#selector(drawBatches) withObject:nil afterDelay:1];
}
}
}
The node contains other data, (a couple of arrays, custom object) and I've tried running the app with all that data removed. I've tried running on the main thread and background threads. I've tried using BFTask to do things asynchronously. Everything I've tried ends up with the same behaviour - creating these SKNode objects eats up memory in 'Other Processes', until on low memory devices, it crashes.
It might be worth noting, that this behaviour has only started to occur since iOS9.
Basically, what can be using all this memory in 'other processes' and how can I free it?
Update
I've tried running the Sprite Kit sample app, and even that uses ~550MB in other processes when it launches. Could this be a major Sprite Kit bug?
Well it turned out to be a rather specific issue. The memory allocated to other processes was in fact memory leaking from my app. It occurred when I flattened a node with many children, but didn't nil an NSDictionary that contained references to all the pre-flattened nodes. For some reason, this mem leak didn't show up when profiling.
I also found a very good blog post: http://battleofbrothers.com/sirryan/memory-usage-in-sprite-kit on reducing your app's memory footprint. Worth a read if you're trying to optimise.
I want to provide a solution for those who are not necessarily using SpriteKit, but are facing issues with Other Processes taking up more and more memory - meaning there is a leak. This is the best way I've found to debug leaks in 'Other processes' so far.
Open Instruments, select Activity Monitor
Reproduce the steps in your application, see which process is taking ownership for the leak. For example if it is mediaserverd, you probably have a leak revolving around encoding/decoding or something media related, so things like releasing buffers or releasing the decompression session might not be working as planned.
Now that you have an idea of where to look, open Xcode and use the Debug Memory Graph tool, and look for the potential leaking instances, and you should see all the strong references towards it. For myself working a lot in objective-c++ it turns out to be missing autoreleasepools quite often.
I am developing an application on iOS8 based on reactive cocoa. The application mainly does network operations.
I noticed that when all my signals complete and all signal references are nulled, i see a few RAC* objects still alive in the memory when i checked through instruments. Is this intended or is my code leaking memory? When i run the signal, there is an activity surge where i see a lot of RAC objects getting allocated and then it falls back to this state as shown the the below screen capture.
Every subsequent invocation ends in this same state. So i am not very worried about it btw.
http://imgur.com/sCL8Y3p
Thanks,
Those are all shared global instances that RAC uses so it doesn't need to allocate memory for every use of them. I'm sure there's a fancier word for that optimization, but I can't think what it is. For example, check out RACUnit:
+ (RACUnit *)defaultUnit {
static dispatch_once_t onceToken;
static RACUnit *defaultUnit = nil;
dispatch_once(&onceToken, ^{
defaultUnit = [[self alloc] init];
});
return defaultUnit;
}
Since all RACUnits are the same, RAC never bothers to make more than one instance of it. That's all you're seeing.
I am creating an application with ARC enabled and iOS 7 only. My all properties are properly marked as weak and all strong variables are marked as nil where I need it.
When I run my application with Instruments I found that memory allocation is continous increasing. When I go to any screen the memory increases (approximate 2 MB). When I pop that view the memory gets down to only few KBs. I don't know what happening.
while poping a view I am using following:
UPDATE:
[UIView animateWithDuration:0.5 animations:^{
CGRect newFrame = aSideMenu.view.frame;
newFrame.origin = SIDE_MENU_VIEW_ORIGIN_FINAL;
[aSideMenu.view setFrame:newFrame];
} completion:^(BOOL finished) {
[sender setUserInteractionEnabled:YES];
}];
Here I am using aSideMenu in block. aSideMenu is strong variable. Do you think I need to create it's weak reference and use?
__weak id aWeak = aSideMenu;
and use this aWeak instead of aSideMenu?
Also In few block I am using:
NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:....nil];
Should I pass weak reference of `dict' too?
I am not sure if this is the reason. Please help me to track the issue. Also let me know if anything else needs to add in this question for better solution.
Thanks
It would be great if you paste your code also. Without code I can just give you some tips.
Like never try to access strong pointer of self in block. Before entering in a block create weak pointer of self.
__weak id weakSelf = self;
and then use weakSelf inside the block.
Better also test your app for unbounded memory growth, where allocated memory never get chance to dealloct, you can take footprints by using Allocation instrument.
Update:
YES because you are calling setter method on strong pointer, it will retain it. You have to make them __weak or __block if they are shared.
https://developer.apple.com/library/ios/documentation/cocoa/conceptual/Blocks/Articles/bxVariables.html#//apple_ref/doc/uid/TP40007502-CH6-SW1
After having some more code, I want to make some thing more clear about the referenceing in block.
Memory issue may arrise when you reference some strong pointer inside block, as block will not let them deallocat, as they have valid reference, this is the major reason of memory issues. For that we have we create a weak pointer by using __weak id so I will not create a retian cycle.
But there is another issue if object have no other vaild reference, It will be deallocated and weak reference will be nil and it can cause a crash.
So good practice is to create a strong reference to weak in side the block and check for the nil.
I cannot find any detailed apple documentation on how the NSZombie really functions. I understand that its designed to not actually release objects and just maintain a count of references to catch any extra releases, but how would something like this work:
for(int i = 1; i < 10; i++)
{
NSMutableArray *array = [[NSMutableArray alloc] initWithCapacity: i];
[array release];
}
Since the same variable/object is being allocated/initialized and released in the same application, how would NSZombie's technically handle this? I know that this shouldn't flag any zombies because every alloc has a release, but how would Xcode technically handle re-allocating the same memory with different capacities?
With Zombies, objects don't actually need to be freed[1] -- the object is simply turned into a "Zombie" at some point after the object's retain count reaches 0. When you message a "Zombified" instance, a special error handler is performed.
1) Freeing Zombies is optional. Unless you really need the memory for a long running or memory intensive task, it is a more effective test to not to free the zombies (NSDeallocateZombies = NO)
This question was answered in the comments by Brad Larson.
Quote:
That isn't the same object, or the same memory. You're creating a distinct, new NSMutableArray instance on every pass through that loop. Just because a pointer to each is assigned to array does not make them the same object.
A pointer merely points to a particular location in memory where the object exists. A given object in memory can have multiple pointers to it, or even none (when it is being leaked). NSZombie acts on the object itself, not pointers to it.
I am stuck with the Cocoa Memory Managagment.
- (IBAction) createPush:(UIButton *)sender {
[create setEnabled:NO];
[release setEnabled:YES];
aLocation = [[Location alloc] init];
// Put some Example Stuff in the Class
aLocation.title = #"Apartment";
aLocation.street = #"Examplestreet 23";
aLocation.zip = #"12345";
aLocation.city = #"Exampletown";
aLocation.http = #"http://google.com";
aLocation.info = #"First Info Text";
aLocation.info2 = #"Second Info Text, not short as the first one";
aLocation.logoPath = #"http://google.de/nopic.jpg";
[aLocation.pictures addObject:#"http://google.de/nopic.jpg"];
[aLocation.pictures addObject:#"http://google.de/nopic.jpg"];
}
- (IBAction) releasePush:(UIButton *)sender {
[release setEnabled:NO];
[create setEnabled:YES];
[aLocation release];
aLocation = nil;
}
This Code works fine if I set or get Variables, but when I call the 'last' release (so the retain count is 0) it dealloc Method of aLocation gets called, but in Instruments Allocations you see that no memory is given back.
Here the Sources of Location:
http://homes.dnsalias.com/sof/Location.m
same Link with a '.h' instead of '.m' for the Header file (sorry its because of the Spaming Rule).
And the whole Project: http://homes.dnsalias.com/sof/Location.zip
Thanks for any help, where is my failure? Dennis
This Code works fine if I set or get
Variables, but when I call the 'last'
release (so the retain count is 0) it
dealloc Method of aLocation gets
called, but in Instruments Allocations
you see that no memory is given back.
What do you mean by "no memory is given back"?
Though oddly named, the memory management of aLocation is correct is the above code (assuming you have released it in dealloc as well).
Why doesn't memory use decrease when a single object is released?
(Paraphrased)
It is likely that your object is relatively tiny and, thus, that single deallocation falls below the ~20K or so needed to show up in Instruments.
If your app is crashing due to memory use issues, looking to a single deallocation is the wrong place to start. The first thing to do is to answer why your app is accreting memory and what is responsible for that growth.
Configure the Allocations instrument to only track live allocations. Then sort by total memory use. That'll show you what type of allocation is consuming the most memory. Start by reducing that.
Heapshot analysis can be very effective in these situations.
Additional Infos here because of maximum number of links and I have'nt the opportunity to post images...
What do you mean by "no memory is given back"?
I will show you the Instruments run, then it should be clear.
Screenshots from Instruments run
If want more Detail klick here for Instruments Run.
Your code is just fine. You are mistaken the output from Instruments. There is no Location object leaking.
For leaks, use the "Leaks" instrument. It won't fire. :-)