Detect application heap size in Android

Question

How do you programmatically detect the application heap size available to an Android app   I heard there s a function that does this in later versions of the SDK  In any case  I m looking for solution that works for 1 5 and upwards

User · Answer

The official API  is      This was introduced in 2 0 where larger memory devices appeared   You can assume that devices running prior versions of the OS are using the original memory class  16

User · Answer

There are two ways to think about your phrase  application heap size available     How much heap can my app use before a hard error is triggered   And How much heap should my app use  given the constraints of the Android OS version and hardware of the user s device    There is a different method for determining each of the above   For item 1 above  maxMemory    which can be invoked  e g   in your main activity s onCreate   method  as follows   Runtime rt   Runtime getRuntime    long maxMemory   rt maxMemory    Log v  onCreate    maxMemory     Long toString maxMemory      This method tells you how many total bytes of heap your app is allowed to use   For item 2 above  getMemoryClass    which can be invoked as follows   ActivityManager am    ActivityManager  getSystemService ACTIVITY SERVICE   int memoryClass   am getMemoryClass    Log v  onCreate    memoryClass     Integer toString memoryClass      This method tells you approximately how many megabytes of heap your app should use if it wants to be properly respectful of the limits of the present device  and of the rights of other apps to run without being repeatedly forced into the onStop     onResume   cycle as they are rudely flushed out of memory while your elephantine app takes a bath in the Android jacuzzi   This distinction is not clearly documented  so far as I know  but I have tested this hypothesis on five different Android devices  see below  and have confirmed to my own satisfaction that this is a correct interpretation   For a stock version of Android  maxMemory   will typically return about the same number of megabytes as are indicated in getMemoryClass    i e   approximately a million times the latter value    The only situation  of which I am aware  for which the two methods can diverge is on a rooted device running an Android version such as CyanogenMod  which allows the user to manually select how large a heap size should be allowed for each app   In CM  for example  this option appears under  CyanogenMod settings     Performance     VM heap size    NOTE   BE AWARE THAT SETTING THIS VALUE MANUALLY CAN MESS UP YOUR SYSTEM  ESPECIALLY if you select a smaller value than is normal for your device   Here are my test results showing the values returned by maxMemory   and getMemoryClass   for four different devices running CyanogenMod  using two different  manually-set  heap values for each    G1    With VM Heap Size set to 16MB    maxMemory  16777216 getMemoryClass  16  With VM Heap Size set to 24MB    maxMemory  25165824 getMemoryClass  16   Moto Droid    With VM Heap Size set to 24MB    maxMemory  25165824 getMemoryClass  24  With VM Heap Size set to 16MB    maxMemory  16777216 getMemoryClass  24   Nexus One    With VM Heap size set to 32MB    maxMemory  33554432 getMemoryClass  32  With VM Heap size set to 24MB    maxMemory  25165824 getMemoryClass  32   Viewsonic GTab    With VM Heap Size set to 32    maxMemory  33554432 getMemoryClass  32  With VM Heap Size set to 64    maxMemory  67108864 getMemoryClass  32     In addition to the above  I tested on a Novo7 Paladin tablet running Ice Cream Sandwich  This was essentially a stock version of ICS  except that I ve rooted the tablet through a simple process that does not replace the entire OS  and in particular does not provide an interface that would allow the heap size to be manually adjusted   For that device  here are the results    Novo7   maxMemory  62914560 getMemoryClass  60    Also  per Kishore in a comment below     HTC One X   maxMemory  67108864 getMemoryClass  64    And  per akauppi s comment     Samsung Galaxy Core Plus   maxMemory   Not specified in comment  getMemoryClass  48 largeMemoryClass  128    Per a comment from cmcromance    Galaxy S3  Jelly Bean  large heap   maxMemory  268435456 getMemoryClass  64    And  per tencent s comments     LG Nexus 5  4 4 3  normal   maxMemory  201326592 getMemoryClass  192  LG Nexus 5  4 4 3  large heap   maxMemory  536870912 getMemoryClass  192  Galaxy Nexus  4 3  normal   maxMemory  100663296 getMemoryClass  96  Galaxy Nexus  4 3  large heap   maxMemory  268435456 getMemoryClass  96  Galaxy S4 Play Store Edition  4 4 2  normal   maxMemory  201326592 getMemoryClass  192  Galaxy S4 Play Store Edition  4 4 2  large heap   maxMemory  536870912 getMemoryClass  192    Other Devices   Huawei Nexus 6P  6 0 1  normal   maxMemory  201326592 getMemoryClass  192    I haven t tested these two methods using the special android largeHeap  true  manifest option available since Honeycomb  but thanks to cmcromance and tencent we do have some sample largeHeap values  as reported above   My expectation  which seems to be supported by the largeHeap numbers above  would be that this option would have an effect similar to setting the heap manually via a rooted OS - i e   it would raise the value of maxMemory   while leaving getMemoryClass   alone  There is another method  getLargeMemoryClass    that indicates how much memory is allowable for an app using the largeHeap setting   The documentation for getLargeMemoryClass   states   most applications should not need this amount of memory  and should instead stay with the getMemoryClass   limit    If I ve guessed correctly  then using that option would have the same benefits  and perils  as would using the space made available by a user who has upped the heap via a rooted OS  i e   if your app uses the additional memory  it probably will not play as nicely with whatever other apps the user is running at the same time    Note that the memory class apparently need not be a multiple of 8MB   We can see from the above that the getMemoryClass   result is unchanging for a given device OS configuration  while the maxMemory   value changes when the heap is set differently by the user   My own practical experience is that on the G1  which has a memory class of 16   if I manually select 24MB as the heap size  I can run without erroring even when my memory usage is allowed to drift up toward 20MB  presumably it could go as high as 24MB  although I haven t tried this    But other similarly large-ish apps may get flushed from memory as a result of my own app s pigginess   And  conversely  my app may get flushed from memory if these other high-maintenance apps are brought to the foreground by the user   So  you cannot go over the amount of memory specified by maxMemory     And  you should try to stay within the limits specified by getMemoryClass     One way to do that  if all else fails  might be to limit functionality for such devices in a way that conserves memory     Finally  if you do plan to go over the number of megabytes specified in getMemoryClass    my advice would be to work long and hard on the saving and restoring of your app s state  so that the user s experience is virtually uninterrupted if an onStop     onResume   cycle occurs     In my case  for reasons of performance I m limiting my app to devices running 2 2 and above  and that means that almost all devices running my app will have a memoryClass of 24 or higher   So I can design to occupy up to 20MB of heap and feel pretty confident that my app will play nice with the other apps the user may be running at the same time   But there will always be a few rooted users who have loaded a 2 2 or above version of Android onto an older device  e g   a G1    When you encounter such a configuration  ideally  you ought to pare down your memory use  even if maxMemory   is telling you that you can go much higher than the 16MB that getMemoryClass   is telling you that you should be targeting   And if you cannot reliably ensure that your app will live within that budget  then at least make sure that onStop     onResume   works seamlessly   getMemoryClass    as indicated by Diane Hackborn  hackbod  above  is only available back to API level 5  Android 2 0   and so  as she advises  you can assume that the physical hardware of any device running an earlier version of the OS is designed to optimally support apps occupying a heap space of no more than 16MB   By contrast  maxMemory    according to the documentation  is available all the way back to API level 1   maxMemory    on a pre-2 0 version  will probably return a 16MB value  but I do see that in my  much later  CyanogenMod versions the user can select a heap value as low as 12MB  which would presumably result in a lower heap limit  and so I would suggest that you continue to test the maxMemory   value  even for versions of the OS prior to 2 0   You might even have to refuse to run in the unlikely event that this value is set even lower than 16MB  if you need to have more than maxMemory   indicates is allowed

User · Answer

Some operations are quicker than java heap space manager  Delaying operations for some time can free memory space  You can use this method to escape heap size error  waitForGarbageCollector new Runnable        Override   public void run            Your operations                  Measure used memory and give garbage collector time to free up some    of the space         param callback Callback operations to be done when memory is free      public static void waitForGarbageCollector final Runnable callback       Runtime runtime    long maxMemory    long usedMemory    double availableMemoryPercentage   1 0    final double MIN AVAILABLE MEMORY PERCENTAGE   0 1    final int DELAY TIME   5   1000     runtime       Runtime getRuntime       maxMemory       runtime maxMemory       usedMemory       runtime totalMemory   -     runtime freeMemory       availableMemoryPercentage       1 -      double  usedMemory       maxMemory     if  availableMemoryPercentage  lt  MIN AVAILABLE MEMORY PERCENTAGE        try         Thread sleep DELAY TIME         catch  InterruptedException e          e printStackTrace              waitForGarbageCollector        callback       else          Memory resources are available  go to next operation      callback run

User · Answer

Here s how you do it   Getting the max heap size that the app can use   Runtime runtime   Runtime getRuntime    long maxMemory runtime maxMemory      Getting how much of the heap your app currently uses   long usedMemory runtime totalMemory   - runtime freeMemory      Getting how much of the heap your app can now use  available memory     long availableMemory maxMemory-usedMemory    And  to format each of them nicely  you can use   String formattedMemorySize Formatter formatShortFileSize context memorySize

User · Answer

This returns max heap size in bytes   Runtime getRuntime   maxMemory     I was using ActivityManager getMemoryClass   but on CyanogenMod 7  I didn t test it elsewhere  it returns wrong value if the user sets heap size manually

User · Answer

Do you mean programatically  or just while you re developing and debugging  If the latter  you can see that info from the DDMS perspective in Eclipse  When your emulator  possibly even physical phone that is plugged in  is running  it will list the active processes in a window on the left  You can select it and there s an option to track the heap allocations

User · Answer

Debug getNativeHeapSize   will do the trick  I should think   It s been there since 1 0  though   The Debug class has lots of great methods for tracking allocations and other performance concerns   Also  if you need to detect a low-memory situation  check out Activity onLowMemory

User · Answer

Runtime rt   Runtime getRuntime    rt maxMemory     value is b  ActivityManager am    ActivityManager  getSystemService ACTIVITY SERVICE   am getMemoryClass     value is MB

User · Answer

Asus Nexus 7  2013  32Gig  getMemoryClass   192 maxMemory   201326592  I made the mistake of prototyping my game on the Nexus 7  and then discovering it ran out of memory almost immediately on my wife s generic 4 04 tablet  memoryclass 48  maxmemory 50331648   I ll need to restructure my project to load fewer resources when I determine memoryclass is low  Is there a way in Java to see the current heap size    I can see it clearly in the logCat when debugging  but I d like a way to see it in code to adapt  like if currentheap  maxmemory 2  unload high quality bitmaps load low quality

[android] Detect application heap size in Android

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