Debug.GC() freeze/reboot

[Mike]

@Reinhard Ostermeier

@Mike

With thousands of objects GC might be running out of memory. Might be due to the way GC determines if objects are still being referenced. Recursion might be used, resulting in memory overflow. Time to look at the code in the porting kit.

Might be worth while to chain blocks, each containing multiple objects, resulting in a shorter chain.

You might want to try to increase the capacity of an ArrayList right after creation to the maximum number of object to be supported. Will avoid memory issues due to dynamically increasing the capacity of the ArrayList.

Multiple linked lists are not the solution.
My tests showed for that a single list with 5000 elements is no problem.
But two lists with 200 elements each GC will freeze.

I meant that you chain blocks, not the items within the blocks.

[taylorza]

@Reinhard Ostermeier

@ taylorza - I’m aware of the Capacity property, but it’s hard to set it if you don’t know how many items you well get in advance (don’t want to loose too much RAM.

You missed my point, I was not trying to tell you anything about using Capacity, I was explaining the 700KB allocation limit and used Capacity as an example.

Mike suggestion to chain blocks is a good suggestion as it will avoid the single allocation size limit. Each block might be an ArrayList of items.

[Reinhard_Ostermeier]

I’ll try different approches and post the results.

[taylorza]

@ Reinhard Ostermeier - Here is a quick example

This runs on the G400

Note:
[ol]I have pushed this to 20000 instances created on each load and it worked
The complete ICollection, IList & IEnumerable implementation for LargeArrayList is left as an exercise for the reader.[/ol]

using System;
using Microsoft.SPOT;
using System.Collections;

namespace MFConsoleApplication1
{
    public class Program
    {
        public static void Main()
        {
            
            Debug.EnableGCMessages(false);
            uint waterMark = Debug.GC(true);
            Debug.Print("Memory:" + waterMark);

            var loader1 = new Loader();
            loader1.CreateSome();
            Debug.GC(true);

            var loader2 = new Loader();
            loader2.CreateSome();
            Debug.GC(true);

            Debug.Print("Memory Used:" + (waterMark - Debug.GC(true)));
            
            Debug.Print(
                Resources.GetString(Resources.StringResources.String1));
        }
    }

    public class Loader
    {
        public void CreateSome()
        {
            for (int n = 0; n < 400; ++n)
            {
                _data.Add(new KmaParam() { TelegramNo = n });
            }
        }

        LargeArrayList _data = new LargeArrayList();
    }

    internal class KmaParam
    {
       public int TelegramNo;
    }
 

    public class LargeArrayList
    {
        private const int ItemsPerBlock = 256;

        private ArrayList _items = new ArrayList();
        private ArrayList _currentBlock;
        private int _count;


        public void Add(object item)
        {
            if (_currentBlock == null || _currentBlock.Count == ItemsPerBlock)
            {
                _currentBlock = new ArrayList();
                _items.Add(_currentBlock);
            }
            _currentBlock.Add(item);
            _count++;
        }

        public object this[int index]
        {
            get
            {
                if (index < 0 || index >= _count) throw new ArgumentOutOfRangeException("index");
                int block = index / ItemsPerBlock;
                int blockIndex = index % ItemsPerBlock;
                return ((ArrayList)_items[block])[blockIndex];
            }
        }
    }
}

[Reinhard_Ostermeier]

@ taylorza - Thanks a lot, I’ll give it a try. If it works for me I complete it and pot on codeshare.

[taylorza]

@ Reinhard Ostermeier - It is a pleasure, I hope it gets you in a position to ship your product! And credit to @ Mike, I believe this is actually what he was explaining or at least something similar.

[Reinhard_Ostermeier]

@ taylorza - I have posted my implementation here:
https://www.ghielectronics.com/community/codeshare/entry/831
It’s tested by sample code and my project.
I have chosen to not implement IList because of Insert and Remove methods.
So it ‘only’ supports ICollection++.

[Dat_Tran]

@ Reinhard Ostermeier -

Since you found out solution, so we will keep it as lower priority.

[taylorza]

@Reinhard Ostermeier

I have chosen to not implement IList because of Insert and Remove methods.
So it ‘only’ supports ICollection++.

I am glad that help!

If you kept it as ArrayList of ArrayLists you would find that Insert and Remove are actually quite easy to implement.

[Reinhard_Ostermeier]

@taylorza

@Reinhard Ostermeier

I have chosen to not implement IList because of Insert and Remove methods.
So it ‘only’ supports ICollection++.

I am glad that help!

If you kept it as ArrayList of ArrayLists you would find that Insert and Remove are actually quite easy to implement.

It’s not that I fear the implementation, but imagine inserting a new item at the beginning of a 5000 item list. Even when using a ArrayList of ArrayLists you Need to move one item over all lists to keep the block size constant.
Thats’s not very performant.
I wanted to create the optimal solution for a straight forward list. Write once read often.