Unity c# List memory leak

Question

I'm getting a serious memory leak when assigning textures at runtime.

When useNewArray is true, Task manager shows that Unity's memory usage grows by ~20 MBs / second.

The full (183k zipped) project can be downloaded here: https://goo.gl/axFJDs

Here's my code:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class testMemory : MonoBehaviour {

public bool             useNewList = false;
Texture2D               newTexture;
public byte             color;
List<Color>             newColors;
List<byte>              staticPixelColorsList;
Color                   tempColor = Color.white;

// Use this for initialization
void Start () {

    newTexture = new Texture2D(0,0);
    newColors = new List<Color>();
    staticPixelColorsList = new List<byte>(120000);
    GetComponent<Renderer>().material.mainTexture = newTexture;
}

// Update is called once per frame
void Update () {

    // Make sure we're using different colors for every frame
    color = (byte)((Time.time*255) % 255);

    if(useNewList)
    {
        // This option causes a memory leak, but it's the one I need 
        // because I'm getting the texture data from an external source
        int newWidth  = Random.Range(200,400);
        int newHeight = Random.Range(200,400);

        // Create a new list each time
        List<byte> newPixels = new List<byte>(newWidth * newHeight);
        for(int i = 0; i < newWidth * newHeight; i++)
        {
            newPixels.Add ((byte)(color * i / 120000f));
        }
        setTexture(newPixels, newWidth, newHeight);

        // Clear the list (yeah, right)
        newPixels.Clear ();
    }
    else
    {
        // Use the same list, but assign new colors
        for(int i = 0; i < 120000; i++)
        {
            staticPixelColorsList.Add ((byte)(color * i / 120000f));
        }
        setTexture(staticPixelColorsList, 300, 400);
        staticPixelColorsList.Clear ();
    }
}

void setTexture(List<byte> inputPixels, int inputWidth, int inputHeight)
{
    newTexture.Resize(inputWidth, inputHeight);

    float colorValue;

    // Convert input value to Unity's "Color"
    for(int n = 0; n < newTexture.width * newTexture.height ; n++)
    {
        colorValue = inputPixels[n] / 255.0f;
        tempColor.r = tempColor.g = tempColor.b = colorValue;
        newColors.Add (tempColor);
    }

    // Actually set the texture pixels
    newTexture.SetPixels(newColors.ToArray());
    newTexture.Apply();
    newColors.Clear();
}
}

Thanx in advance.

Answer 1

Apparently this is a bug with Texture2D.Apply(). It's so deep, Unity's profiler did not show the leak, but external tools did. Unity have acknowledged the problem and are seeking out a solution. No date was given. Thanks for the help :-)

Answer 2

According to this MSDN Article, the List<T>.Clear method resets the Count property to 0 and releases all references to elements of the collection.

However, the capacity remains unchanged. Therefore, the same amount of memory stays allocated. To release this memory, the TrimExcess method should be called, or the Capacity property manually set.

Maybe instead of making a new newPixels list each time the Update method is called you could create this list outside of the function (perhaps in the class declaration) and refill it each time the Update method is called? Clearing would be optional, since every call, the contents would be overwritten. This could also improve performance, since your code won't have to release every member of the collection at the end of every update.