While profiling my iOS app I perform a simple task multiple times where I push and pop a view from the stack, and then take a heapshot. The same code is executed each time and the pushed view just contains some images which get removed as soon as the view gets popped.
Now because the persistent count is 0 for almost half of the heapshots, would it be safe to assume there is no abandoned memory?
I've heard that the rows with a persistent count greater than zero could be because of some internal caching.
I am using Xcode 4.2.1 and the app is using ARC.
Edit:
Thanks to Kendall Helmstetter Gelner I've managed to debug this problem further. I probably shouldn't have been using the simulator for debugging this. I've now run it on the device and it now looks like there is one object which isn't getting released:
After looking through the extended detail view I think I've just about found the cause of the problem.
It's hard to say from just that screenshot what might be cached or not - UIImage will cache things, possibly some other system elements too. It looks like you might be running that in the simulator, have you tried heapshot on a device?
You could also select "Hide System Libraries" to the side and get a better idea how much of your own code is involved.
Related
I'm having a memory issue with one specific ViewController and memory. When I launch my app in debug mode, it launches with 40mb memory usage. (I have no idea if this is already a lot or not -- what is common?). Then, when I open this specific view, it spikes up to about 120mb. The issue is, when I pop this view (with the navigationController popViewController), the memory stays up at 120mb. And then, when I re-open it, it spikes to 200mb (a 80mb increase every time).
With other similar ViewController it spikes up to 120mb too, but when I close the view, it goes back down to more or less 40mb.
The problem is that this specific view contains quite a bit of code (about 1000 lines...) and it's impossible for me to post everything here.
What methods should I use to specifically locate the issue in xCode?
For anyone I might be able to help with this:
use the tools in xCode as recommended. There are some great tutorials online.
In my case it was an issue with an [NSTimer] which kept a strong reference to my view, so it never got released afterwards, thus stacking up memory. Make sure to stop your time when you pop a view.
I'm new to iOS development.
I'm building a simple bus schedule app that makes a HTTP request, parse XML, and display/save data. I have four table view controllers and two view controllers.
When I start the app, Xcode memory report tells me that its memory usage is ~18MB, which is weird since it's just a simple app. I've looked at similar apps on the app store but they were all less than 10MB. Since it's a bus schedule app, I have it make new requests every 30 seconds to update the time. I noticed that each time I change view to look at another schedule, the memory usage increases and it may go up to 50MB or more.
I looked at Xcode's instrument and it looked like there was no leaks. I also looked at allocations and it looked like live bytes kept increasing every time I switched views.
I am kinda stuck from what to do from here. Can anyone guide me please? Thanks in advance.
Use Heapshot to find memory creep. (see: bbum blog)
Basically, their method is to run the Instruments allocate tool, take a heapshot, run an iteration of your code and another heapshot, repeating 3 or 4 times. This will indicate memory that is allocated and not released during the iterations.
In this case, take a heapshot (called something different now) between downloads.
To figure out the results, disclose to see the individual allocations.
If you need to see where retains, releases, and autoreleases occur for an object use Instruments:
Run in Instruments, in Allocations set "Record reference counts" to on (you will have to stop recording to set the option). Allow the problem code to run, stop recording, then search for the object of interest. After that, you'll need to drill down and you will be able to see where all retains, releases and autoreleases occurred.
First, take a look at heap shots as #Zaph suggested. Well worth your while in terms of seeing what's being allocated and not released.
Another technique I use is to use instruments filtering options to filter the display for just the classes in my app. Then, I look for classes which have unusual number's of living instances. For example, most view controllers usually have only one active instance. If there are more, then something is retaining them. Blocks and notification listeners are often the cause.
In your example screen shot, I noticed two things that I would investigate.
Firstly, you have 365 living core animations taking some 30M. Not sure why, but worth thinking about.
Secondly, near the bottom, I noticed 166 table view cell scroll views. Sounds like a lot. I can't see how many living table view controllers you have, but I'm wondering if they are not reallocing. Filtering this list will help establish what's not being dealloc'd.
Finally, leaks can be useful in finding issues, but most of the time what we would regard as a leak looks ok to instruments. So, looking at memory and numbers of allocated instances is a far better guide to finding where things are not being dealloc'd.
Hard to say without any code, but it looks like you have a retain cycle somewhere.
Try to add a dealloc method to the view controllers and make sure that you enter it whenever the view controller disappears.
You say that you make a new request every 30 seconds. If you use a timer with the view controller as a target, the timer has a strong reference to the view controller and vice versa. You have to invalidate the timer when your view controller disappears.
I just started learning the instruments tool, and I'm pretty sure what I am seeing is not good. When I look at allocations, specifically the column "Live Bytes" and "Overall Bytes", I see the number continually increases as the app runs...
My app has two view controllers. A table view, and the second view controller displays detailed information about the row they selected in the table view, downloaded from the internet.
I kept clicking a row in the table view, followed by clicking the back button in the navigation bar... and LiveBytes continued to increase.
I'm guessing this means that my objects aren't being released from memory... but please correct me if I'm wrong.
MY QUESTION IS: How do I use the data in instruments/allocations to track down this memory issue? How do I find the objects not being released from memory?
I'm looking for tips on how to use these tools to clean up any memory problems my app has.
Thanks!
XCODE 4.2.1, deploying to iOS 5.0+
EDIT: I'm looking at the #living column and seeing objects like UIScrollView continuously increase... and never decrease. When I click the back button in a navigation bar, are objects automatically released from memory? When are objects released, or do I need to do it manually? Or could I be running into an issue due to using strong pointers, causing objects to not be released?
Whenever you want to observe memory usage in a cyclic pattern, there's the wonderful Heapshot analysis in the "Allocations" instrument.
Start your app and go to a default state.
In Instruments, press the "Mark Heap" button to create the "Baseline".
Do something in your app like pushing a view controller.
Return to the default state.
Press the "Mark Heap" button again to create a heapshot.
Repeat about five times from step 3.
This will result in a list of heapshots, each showing the objects that are still alive from that cycle. If your app has no leaks there will be no objects left in the middle heapshots.
The first one or two cycles might have warmed up some caches, the last two might not have cleaned up some reused resources. That's why it's usually a good idea to make four to six heapshots.
The magic in the heapshot analysis lies in the fact that the heapshots show you the leaked objects from previous cycles and remove them automatically when the objects are released later. In contrary to the "Leaks" instrument it also finds abandoned memory, not only leaks.
Most Probably you have discarded the arm64 and are running your app with armv7 only. Add both arm64 and armv7 as architectures
I think one of the best ways to solve memory issues is to use ARC.
Edit -> Refactor -> Upgrade to Objective-C ARC.
ARC will handle the majority of memory management in your app. Especially sice your app doesn't sound too complex, it might totally eliminate your problem. You still need to watch out for retain cycles and listen to memory warnings though. If you don't want to use ARC (which you should) at least run the static analyzer. Your problem might be something simple that the static analyzer can show you how to fix.
Edit:
You mentioned scroll views- this might be your problem: Memory leak every time UIScrollView is released
The profile tool has an instrument called 'Leaks'. It is similar to the 'Allocations' instrument but it shows you the object that was not released. May be you can use the 'Leaks' tool to find what is the object that was retained and release these object.
I have an iPad app (IOS 4.3 & 5.0) that is creating a UIView with at least 2 subviews every time the user pages forward or backward. The 2 subviews are UIWebView objects.
On every relevant swipe the old UIWebViews are removed and deallocated properly (removeFromSuperview then stopLoading and set delegate to nil) and the parent UIView is deallocated. I can confirm that both parent UIView and the 2 child UIWebViews are absolutely gone.
I can see the retain count on the webviews as they are being removed and I am quite sure that they are indeed removed every time.
However my memory allocation continues to increase on every swipe by ~200-350k . No leaks in instrument but I can see the memory usage going up slowly.
On iPad 1 the app eventually (within 6-10 minutes of moderate usage) receives multiple memory warnings and is terminated. LowMemory crash log...etc is generated.
We use stringByEvaluatingJavaScriptFromString and loadRequest to populate the Webviews. Memory usage creeps up even when nothing is injected or loaded into the webViews.
Is anybody experiencing this kind of behavior with UIWebViews ? Has anyone dealt with this successfully ?
Thoughs, comments & answers would be greatly appreciated.
Try to use Instruments but with the "Allocations" template and watch the "# Living" columns for UIWebView. I usually use it like this:
Profile app with Allocations template
"Warn up" the app by going thru all tabs, scroll around etc.
Press "Mark Heap", this will create a "Baseline" heapshot
Do the thing you think causes objects to stay around
Press "Mark Heap" again, this will create a "Heapshop #" heapshot
Inspect the objects in "Heapshop #" which will show size and number of objects created and alive since the last heapshot.
Goto 4
Not aware of any leak, but if you are destroying and re-creating the same view hierarchy every swipe, why not store the views and re-use them instead?
Regardless of whether they leak, webviews are computationally expensive to set up, so re-using them and just reloading the content should give you a performance boost, and may solve your leak as well.
are you still seeing this issue? I traced something which looks like unbounded memory usage (not necessarily a leak, but I get low memory warnings and eventual process termination) by calling stringByEvaluatingJavaScriptFromString over and over:
[webview stringByEvaluatingJavaScriptFromString:#"something()"];
It seems like there is something odd there.
I have this problem with performance of my iPad app..
For developing, I use MonoDevelop, which takes care of Garbage collecting. Still my questions are rather generic, I'd say.
OK, I use TabBarController with 5 NavigationControllers. Inside nav controllers there are some controllers, whose views are TableViews or ScrollViews. Next child is always just regular view.
I have a few questions:
1) TableViews never scroll smoothly. I have some alpha transparency, but since I did my graphics in Photoshop and not programmatically, this transparency should not cause much problems. It doesn't matter whether I have few or many results in table.
On the other hand, I have ScrollView which serves same purpose, i.e. to be a table with different layout and buttons have Photoshop generated transparency as well. It works perfectly.
For tables I applied DequeueReusableCell() which works fine (I see that memory usage is not increasing after scrolling). So why would tables scroll so jerky?
2) My app supports rotation. When I scroll table or scrollView and simultaneously tilt the device a bit, I get maybe 1 or 2 FPS. What is the best way to implement rotation? As I understand, ShouldAutorotateToInterfaceOrientation has to be overridden in all controllers in NavigationController chain. Also, I need to add observer in View I want some changes to happen. Do I have to use BeginGeneratingDeviceOrientationNotifications() in all views or is it enough to do it in Main.cs? Maybe this slows it down?
3) After some time app starts getting memory warnings and then crashes eventually. I tried to read logs and run app with Instruments, but can't find the cause of crash.
4) What exactly happens to a View popped from NavigationController stack? I can't reuse it. But could it be that Monotouch (or me) doesn't dispose it correctly?
I have almost same app for iPhone without support for rotation which never crashes. I think I'm doing something wrong with this rotation, but I'm not sure what.
Any help will be appreciated the most. So, thank you in advance.
Regards
1 - transparencies are always a problem. Even if you're not rendering the images in code, the phone still needs to do the compositing of the image, and that may take a lot of time. UITableViews have to calculate the final composite image every time a new cell is displayed, or the table is scrolled, while UIScrollViews can calculate only once, since the image won't change. So be very careful about it, turn the transparency off, and check if performance improves.
2 - You shouldn't need to notify every uiview in your application. Receive the notification in the controllers that you want to update only, like for example if you want to rearrange items in the UIViewControllers view.
3 - you have one (or many) memory leaks. My guess is that MonoTouch probably can't garbage collect UIViews or UIViewControllers, because they're still being linked from somewhere in UIKit, like a UINavigationController
4 - UIViews are not disposed by UIKit until the app gets a memory warning notification.
Like Eduardo said, alpha transparency in Views comes at a price. There are some tools that you can use to identify the bottlenecks discussed in these WWDC 2011 talks from:
https://developer.apple.com/videos/wwdc/2011/
iOS Performance and Power Optimization with Instruments
Understanding UIKit Rendering
In the "Debug" menu of the iOS simulator you can find various debugging tools that will color different regions of the screen indicating where some problematic rendering is taking place. The WWDC 2011 talks show what you can do to fix those problems.
For your memory problems, it is very likely that you have something pointing out to your objects around, so you need to make sure those objects are gone. While we currently are not shipping our new profiler for MonoTouch that can show the source of the problem, I wrote a "poor man's" debug utility that will help you narrow down which objects are alive. It is available here:
http://tirania.org/tmp/HttpDebug.cs
Call HttpDebug.Start () from your application and as you run, connect with a web browser to http://localhost:5000 to get a list of live Objective-C objects surfaced to C#. The tool is not perfect and shows a lot of irrelevant data, but it would at least give you an idea of what is going on.