A weird memory heap leak issue on android

1.Alloc a large memory on heap save to _largeHeapObjects list
2.Alloc temp heap every frame for morment
3.Stop frame alloc and clear the _largeHeapObjects the call GC.Collect();
but sometime the managedHeap.UsedSize not set to start size.

Code (CSharp):

1. using System;
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5. using UnityEngine.Profiling;
6. using UnityEngine.Scripting;
7.  
8. public class TestMain : MonoBehaviour
9. {
10.  
11.     public int allocTempHeapSizeBytes = 1024 * 1024 * 10;//10MB
12.  
13.  
14.     private bool AllocLargeMemoryPermanent = false;
15.     private bool AllocLargeMemoryTemp = false;
16.  
17.  
18.     private List<byte[]> _largeHeapObjects = new List<byte[]>();
19.  
20.     void Start()
21.     {
22.         //GarbageCollector.GCMode = GarbageCollector.Mode.Disabled;
23.     }
24.  
25.     // Update is called once per frame
26.     void Update()
27.     {
28.         if(AllocLargeMemoryTemp == true) {
29.  
30.             if( Time.frameCount % 10 == 0) {
31.                 var size = UnityEngine.Random.Range( 1,  allocTempHeapSizeBytes );
32.                 var bytes = new byte[size];
33.                 Array.Clear( bytes, 0, bytes.Length );
34.                 bytes = null;
35.             }
36.  
37.         }
38.     }
39.  
40.     public void onAllocLargeMemoryPermanentOnce() {
41.         AllocLargeMemoryPermanent = true;
42.         var amount = 1024 * 1024 * 1;
43.         var itemSize = 512;
44.         _largeHeapObjects = new List<byte[]>( amount );
45.         for (int i = 0; i < amount; i++) {
46.             _largeHeapObjects.Add(new byte[itemSize]);
47.         }
48.         GC.WaitForPendingFinalizers();
49.     }
50.  
51.     public void onAllocLargeMemoryTempEveryNFrame() {
52.         AllocLargeMemoryTemp = true;
53.     }
54.  
55.     public void onStopAllocTempHeap() {
56.         AllocLargeMemoryTemp = false;
57.         if(_largeHeapObjects!=null)
58.             _largeHeapObjects.Clear();
59.         _largeHeapObjects = null;
60.         GC.Collect();
61.         GC.WaitForPendingFinalizers();
62.         Resources.UnloadUnusedAssets();
63.     }
64. }
65.  

 

Thank you for replay.

That is one question puzzled me. Why Boehm GC not recycle the memory that has no referece?

 

Sorry, let me try to ask the question more clearly:
Is it a normal thing:
In some cases,

Profiler.GetMonoUsedSizeLong

（ not the Profiler.GetMonoHeapSizeLong ）
will return a large number( e.g. 100MB ) even though ALL allocation is cleared, no reference, and run GC.Collect() like the sample script above?

Because the video above described a interesting issue, even All objects should be GCed, the Profiler.GetMonoUsedSizeLong still reports the USED heap memory is 100+MB

 

Not exactly. Just pressed button 3 and run clear function

onStopAllocTempHeap

again and again.
The usedmono wouldn't go down.

Anyway, I'll try your code tomorrow.

BTW, the cause ticket id is 1219233.
Many thanks for your reply and interested in this.

 

FYI, double GC don't help much, it still leaks.
And yes, Memory Profile, I have already used it, no any big difference if you compare the normal snapshot(<10MB) and the leaked snapshot(>100MB).
I did this again today for capture the screenshot.

 

I browse the code of boehmgc
I found that it has blacklist.c and it‘s said :

Code (CSharp):

1. /*
2. * We maintain several hash tables of hblks that have had false hits.
3. * Each contains one bit per hash bucket;  If any page in the bucket
4. * has had a false hit, we assume that all of them have.
5. * See the definition of page_hash_table in gc_private.h.
6. * False hits from the stack(s) are much more dangerous than false hits
7. * from elsewhere, since the former can pin a large object that spans the
8. * block, even though it does not start on the dangerous block.
9. */

It seems like the 2 that you point out.

 

Anyone got this problem solved? i have a similar situation, in editor my script runs well but in android il2cpp build it does not seems to free memory.

 

I have similar problem. Memory leak on Android build, fine on PC+Editor.
But instead of manual allocations, I just create Texture2D many times.

I have main screen (scene 1) and game scene (scene2) with a lot of Texture2D objects.

When moving between scenes (scene 1 -> scene 2 -> scene 1 -> scene 2 -> scene1 -> scene2) I get increasing managed heap memory for scene2, which eventually causes application crash on Android device. When I am trying to reproduce in Editor, on PC, there is no memory leak.

How can I fix this / is there some workaround?

Unity 2021.3.26f1.