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.
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I ran the instruments 'Leaks' tool to test if my app has any leaks, and it showed me that I have some leaks. I'm not an expert at fixing leaks, I was wondering if
I have a leak, and
What I should do to fix it.
You would appear to have a leak, but it looks modest. You can click on the little arrows next to the memory address and it should take you a screen in which you can drill in and see where that memory was allocated, which is the first step in figuring out why it wasn't deallocated. (I'd start the non-malloc objects, as more often they map more directly to your code and it's easier to diagnose).
But sometimes you'll see modest leaks like this which are, as Mike Robinson said, false positives. And even if it's not a false positive, it could be coming from the OS, itself, not your code. So we sometimes go through an exercise of really stressing the app (e.g. repeatedly running through the portion of the app that seemed to generate the leak) to see how rapidly the leak grows, if at all. It looks like your your leak might add up to less than 1 kilobyte or so, and doesn't continue to grow, you might choose to not worry about it. (Or at least once you've satisfied yourself that there's nothing in your code that causes it.)
Personally, though, I'm less concerned about these modest leaks than the significant growth in overall memory usage. It might just be an appropriate caching of images, or it might be a sign of some abandoned memory (which leaks tool won't show you). I'd try simulating memory warning and see how much of that memory is recovered. You can also drag across the timeline and go to the allocations view, and you can see what accounts for that memory consumption. You might want to make sure you don't have some deeper memory problem unrelated to the modest leaks reported by "Leaks" tool. Not all memory problems appear in "Leaks": The "Allocations" growth can also indicate problems, and I'd be a little worried that you're not seeing your memory usage drop down to some steady-state level.
Apple shared an example allocation graph, advising us to watch out for the red "wasted" memory. The warmup portion is not so critical, nor is the intermediate level (as long as it's not too high), but the growth of the steady state level is indication of a more serious memory problem:
In your case, I'm not seeing the app return to a steady state at all, which is why I'm a tad concerned. But I'm not sure how much you exercised the app or whether you gave it a chance to return to that steady-state.
If you watch (the somewhat dated, yet still relevant) WWDC 2013 Fixing Memory Issues, it will arm you with tools and techniques for diagnosing and resolving memory issues. It is where the above chart came from and describes it in greater detail. Note, the PDF presentation is nice, but the video is much better, as it includes some practical demonstrations for using Instruments. The WWDC 2012 iOS App Performance: Memory is also good. (It looks like there might be problems streaming the videos, but it looks like you can still download it.)
First of all, there's not a lot of detail I can offer, so I realize this question may seem incomplete. At this stage, I'm really looking for any ideas. Frankly, I'm just baffled by this one.
I'm building a graphics-heavy app that really maxes out the CPU. CPU utilization on the devices tends to be around 150% according to XCode (I know that sounds weird, it seems to be of a possible 200% because of the device having two cores). I've instrumented the tasks that do the most processing so I can see how long they take in the debug output. Also note that I am compiling with -Ofast (aggressive optimizations), even for debug builds.
Here's the weird thing. About 5-10 seconds into running the CPU intensive mode of the app, everything slows down. It's very visible. Because of my instrumentation, I can see that suddenly everything takes about 3 times as long as it did before. It's pretty uniform across all tasks, and it doesn't speed back up. Here's the really weird thing. If I break execution in the debugger and resume, I get another 5-10 seconds of fast execution before it slows down again.
Looking at the CPU and memory usage reported by XCode, everything stays about the same. The app uses no more than 90MB of memory at any point.
Is there a feature of iOS that slows down CPU intensive apps or underclocks the device to conserve battery life? I realize I'm sharing resources with the OS, but this is behavior I can reliably reproduce every time.
Again, I realize my question is vague, and there's no relevant code I can post. Any ideas about causes or even debugging methods are welcome.
First of all, thank you #thst for trying really hard to help me out. My question was kind of dumb since it really could have been anything.
I eventually solved the problem by rendering (via OpenGL, a detail I forgot to include, again showing how bad my question was) only when there is actually a change to the state of the objects and textures being rendered. It used to render at 60FPS all the time.
The app also uses CIDetector to detect faces. I think, but I am not sure, that CIDetector uses the GPU to perform its detection. If so, there might have been some contention for GPU resources. CIDetector blocking on a wait may have caused slowdown throughout the app.
Thanks everyone.
I recently ported a project over to ARC as I was having trouble with crashes and actually determining the cause, whether it was leaks or retain cycles etc., Now I have ported it over, I have not done massive testing to see whether it still crashes as I have not managed to get passed the activity monitor giving me the heeby jeebies when it shows my application doing This (activity monitor profiler)
whereas in allocations tools it looks something like
That real memory usage is not even the worst of it, at one point it shot up to around 90 odd MBs, I am unsure on how to proceed as I am not 100 percent sure what to do with the information given here, Except assume that I might be dong something, very wrong, And I have also run the leaks instrument, I have a few but they are minimal, they are all in bytes.
Does anyone have an explanation? or at the very least are able to clarify what I am possibly looking at? what's the difference between real memory usage and live bytes and overall bytes? Also these results were gotten doing exactly the same actions once and then showing you at the end of it.
I have been trying to reduce the real memory usage as pre ARC conversion I was having memory warnings and silent crashes frequently, I have not run into these again after converting, but I have not done any prolonged testing as I cannot conceive of even trying when the real memory usage looks like that. Which actually looks a lot higher than before ARC...Although the live bytes does look lower post ARC...Madness!
Something that confused me for a while is that ARC - wonderful as it is - does not necessarily avoid the need for #autoreleasepool.
https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmAutoreleasePools.html
I ran very large memory usage in an app until someone suggested:
#autoreleasepool {
// lots of allocating of objects returned from methods then discarded
} // and the closing brace of the autoreleasepool block causes their memory to be recovered here
Maybe that will help you.
A good explanation of the meaning of the various columns in the profiler is at Instruments ObjectAlloc: Explanation of Live Bytes & Overall Bytes
I'm writing a game using Corona for a game design class and though I'm still learning, I've got most of the basics down. Right now, I have a situation where the program slows down after about two minutes or so of playing, and I'm not entirely sure why. I've already implemented code to remove all bodies which have served their purpose and I even have it set up to print a notification when each one is removed.
http://www.mediafire.com/?5fz7ru0c6euwq1k
This is the download link. Any help is greatly appreciated. Thanks!
First off, have you checked the memory usage? If the problem gradually slows down that certainly sounds like a memory leak, but you need to check the memory usage to be sure. Print out memory usage to the console like so:
print("mem "..collectgarbage("count"))
Put that in an enterFrame listener so that you can watch the memory usage continuously while your app is running.
Now once you are seeing the memory consumed by your app, the most crucial step in any sort of debugging is isolating the problem. That is, zero in on the spot in the code that causes the problem. For some problems you can rely on techniques like printing debug messages to the console, but for a memory leak your best bet is often to selectively comment out sections of the code to see what affect that has on memory.
For example, first comment out the event listeners on one screen and then check the memory usage. If the leak is gone, then you know the problem was something to do with those event listeners. If the leak is unaffected, then restore those event listeners and comment out the next possible cause of a memory leak. rinse and repeat
Once you know the exact section of code that is causing the leak, you will probably be able to see what you need to fix. If not, ask about that specific code.
I am creating apps for the Ipad and its driving me crazy.
The memory that is usable by the apps changes depending on what other apps were ran before it.
There is no reliable set amount of memory that can be used by your app.
i.e. If safari is ran then even after it closes it takes up some amount of memory which effects other apps.
Does anyone know if there is a way to clear the memory before my app runs so I can get the same running environment every time?
I have created several prototype apps to show to other people and it seems like after a few days they always come back to me and tell me that it crashes and to fix it.
When I test it, the reason is always because there is not enough memory (when there was enough before when I was testing). So I need to squeeze every bit of memory (which usually effects performance due to heavy loading and releasing) out of the app and tell them to restart their ipad if it continues to happen.
I read in a book that generally apps can use at max 40mb or so, most of the apps that crash are crashing at around 27mb. I want my remaining 13mb!!
While you will get a pretty good state after a reboot, what you really should look for is clean memory management and avoiding leaks.
Using the available memory wisely is solely up to the programmer. Don't tell your users to reboot the device, ever. And with every update of the OS memory things might change anyway.