Is this memory leak?

[King Chan]

Dear Telerik Staff,

I wonder if I did the garbage collection incorrectly, or this is memory leak?
I spent few days to research about Silverlight's memory leak issues and I know it affected Telerik's controls as well, I just want to see if this is caused by same reason or it is just the way I do the garbage collection was wrong.


The demo I created is very simple, Button "Create Obj" will create 10 RadScheduler and add into LayoutRoot and to a List<RadScheduler>.

Then the Button "Collects" will run though the List<RadSchdeduler> to remove each RadScheduler from LayoutRoot, then set each RadScheduler object to null, Clear() the list, then do the: 

GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect(); 

1) Before Click Create Obj Button:
Task Manager:
IExplorer.exe
Memory(Private Working Set): 42,828k
Performance Memory: 656MB

2) After Click Create Obj Button:
Task Manager:
IExplorer.exe
Memory(Private Working Set): 194,828k
Performance Memory: 805MB

3) After Click "Collect" Button:
Task Manager:
IExplorer.exe
Memory(Private Working Set): 194,280k
Performance Memory: 801MB

For same scenario, if I create Button obj(500 Buttons) instead of RadScheduler, I can see the memory increased few MB and released few MB properly.
But again, for same scenario, if I create RadDialog(10 RadDialog with no Content) obj this time instead of RadScheduler, then I close it, null it, GC.Collect it, it will release PART OF the memory, and have around 1 MB didn't release.

And here is the demo code (everything created in MainPage.xaml.cs):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Telerik.Windows.Controls;
using System.Reflection.Emit;
using System.Diagnostics;

namespace RadControlsSilverlightApp4
{
    public partial class MainPage : UserControl
    {

        TextBlock aLabel = new TextBlock();

        List<RadScheduler> SchedulerList = new List<RadScheduler>();
        public MainPage()
        {
            InitializeComponent();
            this.LayoutRoot.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(100, GridUnitType.Auto) });
            this.LayoutRoot.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(100, GridUnitType.Pixel) });
            this.LayoutRoot.RowDefinitions.Add(new RowDefinition { Height = new GridLength(100, GridUnitType.Auto) });
            this.LayoutRoot.RowDefinitions.Add(new RowDefinition { Height = new GridLength(70, GridUnitType.Auto) });
            this.LayoutRoot.RowDefinitions.Add(new RowDefinition { Height = new GridLength(70, GridUnitType.Auto) });
            this.LayoutRoot.RowDefinitions.Add(new RowDefinition { Height = new GridLength(500, GridUnitType.Auto) });

            Button aButton = new Button();
            aButton.Content = "Create Objs";
            aButton.SetValue(Grid.RowProperty, 0);
            aButton.SetValue(Grid.ColumnProperty, 0);
            this.LayoutRoot.Children.Add(aButton);

            Button aCollectButton = new Button();
            aCollectButton.Content = "Collects";
            aCollectButton.SetValue(Grid.RowProperty, 1);
            aCollectButton.SetValue(Grid.ColumnProperty, 0);
            this.LayoutRoot.Children.Add(aCollectButton);

            aLabel.SetValue(Grid.RowProperty, 1);
            aLabel.SetValue(Grid.ColumnProperty, 1);
            aLabel.Text = GC.GetTotalMemory(true).ToString();
            this.LayoutRoot.Children.Add(aLabel);

            Button aUpdateButton = new Button();
            aUpdateButton.Content = "Update";
            aUpdateButton.SetValue(Grid.RowProperty, 2);
            aUpdateButton.SetValue(Grid.ColumnProperty, 0);
            this.LayoutRoot.Children.Add(aUpdateButton);


            aButton.Click +=new RoutedEventHandler(aButton_Click);
            aCollectButton.Click +=new RoutedEventHandler(aCollectButton_Click);
            aUpdateButton.Click += new RoutedEventHandler(aUpdateButton_Click);

        }

        public void aButton_Click (object sender, RoutedEventArgs e){
            Debug.WriteLine("Create 10 Obj");

            for (int i = 0; i < 10; i++)
            {
                RadScheduler aScheduler = new RadScheduler();
                aScheduler.SetValue(Grid.RowProperty, 3);
                aScheduler.SetValue(Grid.ColumnProperty, 1);
                SchedulerList.Add(aScheduler);
                this.LayoutRoot.Children.Add(aScheduler);

            }


            aLabel.Text = GC.GetTotalMemory(false).ToString();
            Debug.WriteLine("Obj Count: " + SchedulerList.Count.ToString());
            Debug.WriteLine("Obj Count: " + this.LayoutRoot.Children.Count.ToString());
        }

        public void aCollectButton_Click(object sender, RoutedEventArgs e)
        {

            for (int i = 0; i < SchedulerList.Count; i++)
            {
                this.LayoutRoot.Children.Remove(SchedulerList[i]);
                SchedulerList[i].DataContext = null;
                SchedulerList[i] = null;
            }
            SchedulerList.Clear();

            Debug.WriteLine("Collect!");
            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();
            Debug.WriteLine("Collected!");
            Debug.WriteLine("Obj Count: " + SchedulerList.Count.ToString());
            Debug.WriteLine("Obj Count: " + this.LayoutRoot.Children.Count.ToString());
            aLabel.Text = GC.GetTotalMemory(false).ToString();

        }


        public void aUpdateButton_Click(object sender, RoutedEventArgs e)
        {
            Debug.WriteLine("Update!");
            Debug.WriteLine("Obj Count: " + this.LayoutRoot.Children.Count.ToString());
            aLabel.Text = GC.GetTotalMemory(false).ToString();

        }
    }
}

=========
Update: I just used WeakReference to check, I realize none of the RadScheduler get collected, they are all Alive.
And for the RadDialog, I can see few of the RadDialog object is Alive, and others was got collected, it happens if I try keep clicking Create and Collect frequently. (i.e Created like 500 RadDialog on screen, after collects, there is 3 alives)
=========
Thanks for your help,
King

[Hristo]

Hello King Chan,

Unfortunately Silverlight 4 GDR1 did not fix all memory leaks. We are in a process of preparing Q2 Service Pack 2 (which workarounds known framework leaks and also fix few memory leaks caused by our code).
It will be official in a week or two.

Let us know if you need more information.

Greetings,
Hristo
the Telerik team

[King Chan]

Thanks for your reply, I guess that's mean I didn't did wrong on collecting?
I am still new to silverlight, just want to make sure.

[Hristo]

Hi King Chan,

When testing for memory leaks I don't observe Task Manager (working set). Garbage collection is not something that can be controlled. The correct approach is to create WeakReferences.

I hope that this will help you.

All the best,
Hristo
the Telerik team