I have an app that I am building for iOS 7 only and running on an iPhone 5S. The app sometimes in normal use just freezes up and won't recognize any touch interactions happen and it requires the app to be force quit. I have noticed it doing many different tasks and in different views. I have had this problem while debugging and the RAM usage is at about 65 Mb which I think is pretty good, cpu usage is in the single digits and the debugger doesn't register a crash. Where can I go from here in terms of debugging and trying to fix this pretty serious problem?
To put my comment as an answer, usually when your application freezes, it means either the CPU is doing some heavy lifting or your have a deadlock somewhere. As you mentioned that it was the CPU usage was low, my first guess was a deadlock.
Thanks to Leo Natan for suggesting that it was deadlocks, because it was. There was a specific instance where I was saving and fetching from the background thread and there was an easy solution that made it possible for me to stop fetching on the background thread.
For me, it was an endless while loop. Found it out by pausing the process and checking out the stack trace.
Related
I’m having a memory issue. I get an error message “Thread 1: EXC_BAD_ACCESS(code=1,address=…) The error is elusive, and apparently timing-dependent. On my iPad mini, it usually averages about 3 minutes between crashes, on my iPhone SE it averages 10 minutes, and on the simulator it has run for 20 hours without crashing.
I’m not successful in using the Zombie detector. (See below for my experiences with it.) So I’m trying to go over my code with a fine tooth comb to see what might be causing the crash. What are the issues that might cause an allocation error?
My app is multi-threaded. It takes sound from the microphone, processes it, and continuously updates the display with the processed results. It’s written in Swift 3, so I’m not doing any explicit mallocs or frees.
I’m looking for places in the code that might cause an error. The two things I’m looking closest at are weak references and unsafe pointers. Are there any other common programming errors that could trip me up?
(The Zombie detector is useless. The Apple Instruments User Guide says, “For iOS apps, use the Zombies template with the iOS Simulator, rather than a physical device.” I’ve ignored the warning and tried it with my iPad mini, and I can’t get it to crash. Everything runs at about 1/10 speed, and when I pause the recording, my OSX machine gets sluggish as well, displaying the spinning “Wait” cursor for minutes at a time. The total memory allocation goes up and down, but stays within limits, so there is no major memory leak. I’ve also run the Zombies instrument on the simulator as well. It’s equally sluggish, and it still doesn’t crash.)
The issue in this case turns out to be thread safety. If I set a UInt8 variable on one thread and read it on another thread, it can lead to a memory error. The setters and the getters are not thread safe.
(I’ve been programming computers most of my professional life, mostly in C, C++, and Java. I’m familiar with the multi-threading issues in these languages. I’m new to Swift 3. It simply hadn’t occurred to me up to now that setting and getting numeric variables was not an atomic operation — that an ill-timed access could cause a program to crash. I’m going to have to drastically rethink my approach to concurrency with Swift.)
I'm having trouble finding the cause of an unexpected freeze on iOS because, if pausing the debugger, it doesn't actually pause until unfrozen. Does anyone have any idea on how to track down the actual cause of this before it completely locks up the device?
The simplest answer: don't do anything on the main thread that doesn't have to be on the main thread. For a longer answer, you need to use the Time Profiler probe with Instruments to find the hot spots.
I am writing a game in Swift using SpriteKit with Xcode 7.3 on a Mac mini running El Capitan (both updated in last couple of days).
Shortly after I started, my Mac mini started crashing. The error log indicated that a Kernel Panic had occurred likely due to a memory leak & the process was identified as Xcode. Looking at the Activity Monitor, I can see that when this specific app is loaded in Xcode, the memory used by Xcode fairly rapidly increases even though the App is just sitting there doing nothing.
When other apps are loaded & idle, the memory usage stays more or less constant as you would expect. I have Googled for clues for several hours but can find only info. about memory leaks when an App is running & how to detect them with Instruments.
This is a weird one as far as I'm concerned. I do not have any idea how to start to figure out what's causing this other than starting with a fresh project & gradually adding code to see if/where it starts happening again. I would appreciate any ideas other Xcode users may have.
You don't happen to have
skView.showPhysics = true
turned on?
That is know to be causing memory issues exactly as you described.
There are a number of things you can do to start diagnosing this issue. Firstly you say that only one app is doing this. So this would indicate that the problem is an app problem rather than XCode. This is a good thing :-)
Next I would start using the profiler to monitor the memory and allocated objects in the app. try taking snap shots of the memory at regular intervals and look at what has been allocated since the prior snap shot. The profiler can then help you to dig down into the leaking objects and see where they are being retained and released. This might give you the clue you need.
Another thing is try is the profilers leaks monitoring. That also might tell you whats going on inside your app.
Lastly, is there anything in your code that is executing in some sort of loop. Something that animates on the home screen for example. Perhaps that is leaking.
Thanks very much to Drekka & Adrian B for your speedy answers but, as always happens, as soon as I post a question, I stumble across some information that leads to an understanding & (in this case partial) solution. Looking for an answer to a different question, I came across a thread on the Apple Developers Forum where several others are reporting the same issue.
It is related to the use of the SpriteKit Scene Editor. Hence it is app related in that for me it occurred with the only app for which I have ever used the Scene Editor but in reality it is an Xcode bug. What happens is that if the Scene Editor window is open (i.e. the .sks file is selected), even if the scene is blank, Xcode starts to leak memory at a rate of about 1MB/sec. If you close that window, the leakage stops. It happens even if Xcode is minimized. Apparently, it has been reported as a bug. I guess the work around for now is to accept the leakage while you're modifying your scene & then close the editor when you've finished (or do everything in code).
Cheers,
RB
No matter how long I leave the app without touching my cpu doesn't drop below 90% or so. I'm using Parse and I've narrowed it down to Bolts using up the cpu. Is this normal? Is there any way to reduce the usage?
I don't believe I have any endless loops that would cause it.
No, that is not normal, and will drain your users’ batteries. An app that does that is definitely not releasable.
It’s impossible to know how to reduce the usage without much more diagnostic info, but it’s well worth the time to track it down.
A starting point could be to pause the offending thread in the debugger while the CPU is pegged, and see what the code is doing. If it’s inside Parse, as your profile screenshot suggests, that won’t tell you much — but sometimes examining the pegged code in the debugger as it executes reveals info that Instruments does not.
So I just made an app that loads a map with some markers on it. The app has a navigation controller that segue from the main screen to the map and back. While running the app on my phone and simulator i noticed that if i went back and forth between the home screen and the map, the amount of memory that the app was using just kept growing indefinitely. Is there way to assist in the process of memory management (i know the system uses ARC)? Im using the google maps sdk btw.
Thanks!
Does it cause the app to run out of memory and crash?
Or is it using a ton of memory, receiving a memory warning, and dumping said memory?
So, unless it is causing crashes, it may be behaving correctly.
Apple has extensive and well-documented support for diagnosing these kinds of problems. See "Locating Memory Issues in Your App".
Check your codes where using NSThreads and GCD blocks. If there are some places you create plenty of threads, it is recommended to add a autoreleasepool block.
Memory may leak in these situation:
If you are writing a program that is not based on a UI framework, such as a command-line tool.
If you write a loop that creates many temporary objects.
If you spawn a secondary thread.
For reference: Using Autorelease Pool Blocks