Develop Reference

Very high "Maximum memory use" for libgdx game

I've developed a game with libgdx. I've tried to keep memory consumption as low as possible by doing the following:
Use Pooling where possible.
Limit SpriteBatch's size
When I run the game on my phone (Nexus 5x) from Android Studio, my game runs smoothly and it seems that memory consumption is indeed reasonable: The memory consumption is usually under 23MB (I see this via the memory monitor). However, when I go to the memory tab on my phone (Settings --> Memory --> Memory used by apps) I see the following:
A shocking "Maximum memory use" of 1.2 GB for my game. Way above any other app.
My question(s):
What does this number mean? Does this mean that at one point my game took up 1.2 GB of the RAM?
How can that be if the memory monitor never showed a consumption of over 25MB?
Seeing that the game does run smoothly should I try to get this number down? If yes, how can I do this?

You're mixing up native memory (RAM, as shown on the screenshot) and VM memory.
In the memory monitor, you only see the heap (so the memory that was allocated for the VM on which your app is running), but not the actual RAM. This maximum heap size is limited by the system (see e.g. https://stackoverflow.com/a/9940415/1096567 for examples).
Libgdx is using OpenGL via a JNI and is therefore also using the RAM directly.
To investigate your RAM usage in general you need other tools than the Memory Monitor, see e.g.:
How do I discover memory usage of my application in Android?
I don't know your app, but 1.2GB seems a bit high. If you're not using Texture Atlases & the Texture Packer, it's probably a good place to start optimizing. Also be sure to dispose all Disposables (like BitmapFont). Here is a detailed list.

iOS equivalent to increasing heap size

iOS apps (for the most part) is written in Objective-C, which is a subset of C, and is therefore a data managed language, unlike Android/Java.
In Android, you have the ability to increase heap size by simply adding this one line in the XML android manifest:
<application android:largeHeap="true"/>
Is there an iOS version to doing something like this?

Well in iOS you don't have any control over the memory.
It is all managed by the kernel. So you cannot increase the heap size.
As pointed out in the comments, memory management has a different notion in iOS.
You get as many memory as available but if the app uses to much memory it will be killed by the system.
Now that you explained your goal, you shouldn't download large files into memory, this will cause trouble. Instead you should save it directly to the disk as you get the response.

Take a look at Apple's "Memory Usage Performance Guidelines" for an explanation of how iOS doesn't manage swap space.
Although OS X supports a backing store, iOS does not. In iPhone applications, read-only data that is already on the disk (such as code pages) is simply removed from memory and reloaded from disk as needed. Writable data is never removed from memory by the operating system. Instead, if the amount of free memory drops below a certain threshold, the system asks the running applications to free up memory voluntarily to make room for new data. Applications that fail to free up enough memory are terminated.
iOS attempts to provide each application with as much of the device's memory as the OS can spare. However each application is limited to the device's physical memory. There is no option to allocated larger blocks and expect them to be swapped to disk as needed.
Manipulating the heap size in iOS is therefore not a meaningful concept. Each app already has the largest heap the OS can provide. Instead apps must attempt to minimize their memory footprint to remain within the available space on the host device. This means purging in-memory caches in response to memory warnings, streaming access to resources on disk (as #CouchDeveloper suggested in a comment), and minimizing the amount of memory used overall.
As an additional complication iOS attempts to keep memory in use. Unused memory is wasted capacity and users may be better served by the OS keeping more applications suspended and in memory rather than terminated. As a result attempting to measure available free memory does not give a meaningful result. As the device runs low on free memory other applications will reduce their use in response to memory warnings or by being terminated completely.

How heap memory allocation works

I'm working on an app and I have memory issues.
I started to study this thing and I have met Eclipse's debugging system.
I use DDMS's Heap tester to see how much memory my app allocated.
I saw it's about 90%.
Now I made a simple new project, a blank empty activity without any functions or variables. Just a splendid new project.
I ran this heap tester and I saw the results:
Heap size: 10,629 MB
Allocated: 9,189 MB
Free: 1,440 MB
Used: 86.45 %
Objects: 44,565
Well, is it normal?
I have a very simple blank activity, and nothing else, and this app is used 86% of memory?
Allocated 9 MB of 10? Really? Is that normal? How this works?
Please instruct me about this, because I would like to know how these memory allocations work.

Dalvik will initially allocate a certain heap size to your app. In your case, this is around 10 MB. As your app needs more memory, Dalvik will increase the heap size upto the maximum configured size (which is different for different devices). If your app still needs more memory after the maximum is reached, then it will cause a OutOfMemoryException.
To learn more about analyzing memory allocations in Android, check out this excellent article from the Android developers blog:
http://android-developers.blogspot.in/2011/03/memory-analysis-for-android.html

Examining Heap Usage is somewhat tricky but is equally easy. Let's find out how.
So consider a small application. You have Android debugging tools to determine the heap usage and to examine them.
You can check this- memory-analysis-for-android, which have more details of how to analize the application effectively in android.
Let's have a short description here too:
There are two ways to start DDMS-
1) Using Eclipse: click Window > Open Perspective > Other... > DDMS
2) or from the command line: run ddms (or ./ddms on Mac/Linux) in the tools/ directory
Then select your application process from Devices and click "Update Heap".
Now switch to the Heap tab in DDMS.
To see the first update, click the Cause GC button.
You will see something like this:
We can see that our set (the Allocated column) is a little over 20MB. If you do some little flip flop, that number can go up. In small applications, the amount of memory we leak is bounded. In some ways, this can be the worst kind of leak to have, because we never get an OutOfMemoryError indicating that we are leaking.
You can use Heap Dump to identify the problem. Click the Dump HPROF file button in the DDMS toolbar and save the file wherever you want. Then run hprof-conv on it.
Using MAT which is a powerful Memory Analyzer tool-
You can install MAT from SITE which is a stand-alone Memory Analyzer tool and analyze the Heap dumps using it.
NOTE:
If you're running ADT (which includes a plug-in version of DDMS) and have MAT installed in Eclipse as well, clicking the "dump HPROF" button will automatically do the conversion (using hprof-conv) and open the converted hprof file into Eclipse (which will be opened by MAT).
Start the MAT and load the converted HPROF file. Navigate to the Histogram view which shows a list of classes sortable by the number of instances, the shallow heap (total amount of memory used by all instances), or the retained heap (total amount of memory kept alive by all instances, including other objects that they have references to).
If we sort by shallow heap, we can see that instances of byte[] are at the top.
Next, Right-click on the byte[] class and select List Objects > with incoming references. This produces a list of all byte arrays in the heap, which we can sort based on Shallow Heap usage.
Pick one of the big objects, and drill down on it. This will show you the path from the root set to the object - the chain of references that keeps this object alive. Lo and behold, there's our bitmap cache!
MAT can't tell us for sure that this is a leak, because it doesn't know whether these objects are needed or not -- only the programmer can do that. However, looking at the stats it is predictable to know that the cache is using a large amount of memory relative to the rest of the application, so we might consider limiting the size of the cache.
Go this way all along for all, and you will see a tremendous amount of performance optimization.

What you see here is allocated memory and not maximum memory which can be allocated, maximum memory which can be allocated depends upon android version and device to device.
In this case, your apps does not have any high memory requirement, all the files,system and object being used to run the app is very small hence initially android has allocated your app a common initial space,now this space goes on increasing as demand from app increases until its met, or it exceeds maximum heap size defines per app by android, in this scenario your app will crash stating running out of memory as reason.
To read more about memory allocation in android go through below developer link
http://developer.android.com/training/articles/memory.html

Android Service Memory Usage

I have an Android app with a running service.
When I look in the "Running Apps" menu in Android settings, I see that my app memory usage is
between 9-16MB .
I used DDMS Allocation Tracker to see where this is coming from, but all of the objects were less than 500 bytes.
Does it make sense? Any other ways to track my app's memory usage?
Also, I have an SQLite database opened as long as the service is running. Is that an impact on memory as well?
Thanks.

Does it make sense?
It neither makes sense nor doesn't make sense. You can get to "9-16MB" by increments of 500 as easily as you can get there by increments of 5000. Also, AFAIK that allocation tracker does not track everything (e.g., bitmaps on pre-3.0 environments).
Any other ways to track my app's memory usage?
Dump your heap (e.g., using the Dump HPROF File toolbar button in DDMS) and examine the results with the MAT plugin for Eclipse. There was a presentation on this at the 2011 Google I|O conference -- the YouTube video is online. You can use this to track memory leaks.
Is that an impact on memory as well?
Some, I'm sure.
Another issue is actually the service itself. Your objective should be to have that service in memory as little as possible, and only while it is actively delivering continuous value to the user. Ideally, your service is destroyed ~99% of the time.

android performance issue

my android application works well but it's performance(speed) is slow. In my logcat i saw frequent garbage collection operation like
11-02 15:07:20.647: DEBUG/dalvikvm(12571): GC freed 295 objects / 38448 bytes in 93ms
Is this the reason for low performance?? How can i improve my applications performance???
anybody please help

If you use the emulator don't worry - it is slow by itself. GC is not responcible for this i think, 93 ms is time you won't even notice. So try your application at the real phone and if there are preformance issues - use the profiler.

Your application performance in terms of user interface and memory is quite related.
In this case 93ms means that your device could be dropping about 6 frames in the ideal scenario. If the GC is executed often this could be a problem.
The Android ART/Dalvik virtual machine is a version of the Java Virtual Machine where the Garbage Collector implementation is based on generations. This means that your application process has a heap associated separated by different generations where the GC is going to act once a generation is full. You can think of these generations as buckets or arrays of memory.
Once a generation is full the Android virtual machine will start the garbage collector process. As the Android virtual machine can not collect and fragment your application heap while the app process is running the garbage collector event will stop all the threads in your app while the garbage collector is working. That's why your application can be dropping frames if the app garbage collector is invoked so repeatedly.
Here you have an example:
Last week I discovered my app was leaking memory. I discovered this because after 20 minutes using my app I noticed the UI was performing really slow. Closing/opening an activity or scrolling a RecyclerView was really slow. After monitoring some of my users in production using http://flowup.io/ I found this:
The frame time was really really high and the frames per second really really low. You can see that some frames needed about 2 seconds to render :S.
Trying to figure it out what was causing this bad frame time/fps I discovered I had a memory issue as you can see here:
Even when the average memory consumption was close to the 15MB at the same time the app was dropping frames.
That's how I discovered the UI issue. I had a memory leak in my app causing a lot of garbage collector events and that's was causing the bad UI performance because the Android VM had to stop my app to collect memory every single frame.
Looking at the code I had a leak inside a custom view because I was not unregistering a listener registered into a Android Choreographer instance. After releasing the fix, everything became normal :)
If your app is dropping frames due to a memory issue you should review two common errors:
Review if your app is allocating objects inside a method invoked multiple times per second. An example could be creating new instances of an object inside a onDraw custom view method.
Review if your app is registering an instance into the Android SDK but not releasing it. Registering a listener into a bus event could also be possible leak.
Disclaimer: The tool I've been using to monitor my app is under development. I have access to this tool because I'm one of the developers :) If you want access to this tool we will release a beta version soon! You can join in our web site: http://flowup.io/.
If you want to use different tools you can use: traveview, dmtracedump, systrace or the Andorid performance monitor integrated into Android Studio. But remember that this tools will monitor your connected device and not the rest of your user devices or Android OS installations.