MonoTouch - WebRequest内存泄漏和崩溃？

Question

我有一个使用3.5MB文件进行HTTP POST的MonoTouch应用程序,它在我测试的主要平台上非常不稳定(带有OS 3.1.2的iPhone 3G和带有OS 4.2.1的iPhone 4).我会描述我在这里做的事情,也许有人可以告诉我,如果我做错了什么.

为了排除我的应用程序的其余部分,我将其缩小为一个小样本应用程序.该应用程序是一个iPhone OpenGL项目,它只做这个:

1. 在启动时,以30k块分配6MB内存.这模拟了我的应用程序的内存使用情况.
2. 将3.5MB文件读入内存.
3. 创建一个帖子来发布数据.(创建一个WebRequest对象,使用GetRequestStream(),然后写入3.5MB数据).
4. 当主线程检测到发布线程完成时,转到步骤2并重复.

此外,每个帧,我分配0-100k来模拟应用程序做某事.我没有保留对这些数据的任何引用,所以应该收集垃圾.

iPhone 3G结果:该应用程序上传了6​​到8次,然后操作系统将其杀死.没有崩溃日志,但有一个LowMemory日志显示该应用程序已被丢弃.

iPhone 4结果:第11次上传时出现Mprotect错误.

一些数据点:

• 随着应用程序继续上传,仪器不显示内存增加.
• 仪器没有显示任何重大泄漏(总共1千字节).
• 使用一个Stream.Write()调用是以64k块还是一次性写入后置数据并不重要.
• 在开始下一次上传之前,我是否等待响应(HttpWebRequest.HaveResponse)并不重要.
• POST数据是否有效无关紧要.我尝试使用有效的POST数据,我尝试发送3MB的零.
• 如果应用程序没有为每个帧分配任何数据,那么内存耗尽需要更长的时间(但如前所述,我分配每个帧的内存在分配它的帧之后没有被引用,所以它应该是由GC舀起来).

如果没有人有任何想法,我会向Novell提交一个错误,但我想先看看我是否做错了.

如果有人想要完整的示例应用程序,我可以提供它,但我已经粘贴了下面的EAGLView.cs的内容.

using System;
using System.Net;
using System.Threading;
using System.Collections.Generic;
using System.IO;
using OpenTK.Platform.iPhoneOS;
using MonoTouch.CoreAnimation;
using OpenTK;
using OpenTK.Graphics.ES11;
using MonoTouch.Foundation;
using MonoTouch.ObjCRuntime;
using MonoTouch.OpenGLES;

namespace CrashTest
{
    public partial class EAGLView : iPhoneOSGameView
    {
        [Export("layerClass")]
        static Class LayerClass ()
        {
            return iPhoneOSGameView.GetLayerClass ();
        }

        [Export("initWithCoder:")]
        public EAGLView (NSCoder coder) : base(coder)
        {
            LayerRetainsBacking = false;
            LayerColorFormat = EAGLColorFormat.RGBA8;
            ContextRenderingApi = EAGLRenderingAPI.OpenGLES1;
        }

        protected override void ConfigureLayer (CAEAGLLayer eaglLayer)
        {
            eaglLayer.Opaque = true;
        }


        protected override void OnRenderFrame (FrameEventArgs e)
        {
            SimulateAppAllocations();
            UpdatePost();           

            base.OnRenderFrame (e);
            float[] squareVertices = { -0.5f, -0.5f, 0.5f, -0.5f, -0.5f, 0.5f, 0.5f, 0.5f };
            byte[] squareColors = { 255, 255, 0, 255, 0, 255, 255, 255, 0, 0,
            0, 0, 255, 0, 255, 255 };

            MakeCurrent ();
            GL.Viewport (0, 0, Size.Width, Size.Height);

            GL.MatrixMode (All.Projection);
            GL.LoadIdentity ();
            GL.Ortho (-1.0f, 1.0f, -1.5f, 1.5f, -1.0f, 1.0f);
            GL.MatrixMode (All.Modelview);
            GL.Rotate (3.0f, 0.0f, 0.0f, 1.0f);

            GL.ClearColor (0.5f, 0.5f, 0.5f, 1.0f);
            GL.Clear ((uint)All.ColorBufferBit);

            GL.VertexPointer (2, All.Float, 0, squareVertices);
            GL.EnableClientState (All.VertexArray);
            GL.ColorPointer (4, All.UnsignedByte, 0, squareColors);
            GL.EnableClientState (All.ColorArray);

            GL.DrawArrays (All.TriangleStrip, 0, 4);

            SwapBuffers ();
        }


        AsyncHttpPost m_Post;
        int m_nPosts = 1;

        byte[] LoadPostData()
        {
            // Just return 3MB of zeros. It doesn't matter whether this is valid POST data or not.
            return new byte[1024 * 1024 * 3];
        }

        void UpdatePost()
        {
            if ( m_Post == null || m_Post.PostStatus != AsyncHttpPostStatus.InProgress )
            {
                System.Console.WriteLine( string.Format( "Starting post {0}", m_nPosts++ ) );

                byte [] postData = LoadPostData();

                m_Post = new AsyncHttpPost( 
                    "https://api-video.facebook.com/restserver.php", 
                    "multipart/form-data; boundary=" + "8cdbcdf18ab6640",
                    postData );
            }
        }

        Random m_Random = new Random(0);
        List< byte [] > m_Allocations;

        List< byte[] > m_InitialAllocations;

        void SimulateAppAllocations()
        {
            // First time through, allocate a bunch of data that the app would allocate.
            if ( m_InitialAllocations == null )
            {
                m_InitialAllocations = new List<byte[]>();
                int nInitialBytes = 6 * 1024 * 1024;
                int nBlockSize = 30000;
                for ( int nCurBytes = 0; nCurBytes < nInitialBytes; nCurBytes += nBlockSize )
                {
                    m_InitialAllocations.Add( new byte[nBlockSize] );
                }
            }

            m_Allocations = new List<byte[]>();
            for ( int i=0; i < 10; i++ )
            {
                int nAllocationSize = m_Random.Next( 10000 ) + 10;
                m_Allocations.Add( new byte[nAllocationSize] );
            }
        }       
    }




    public enum AsyncHttpPostStatus
    {
        InProgress,
        Success,
        Fail
    }

    public class AsyncHttpPost
    {
        public AsyncHttpPost( string sURL, string sContentType, byte [] postData )
        {
            m_PostData = postData;
            m_PostStatus = AsyncHttpPostStatus.InProgress;
            m_sContentType = sContentType;
            m_sURL = sURL;

            //UploadThread();
            m_UploadThread = new Thread( new ThreadStart( UploadThread ) );
            m_UploadThread.Start();            
        }

        void UploadThread()
        {
            using ( MonoTouch.Foundation.NSAutoreleasePool pool = new MonoTouch.Foundation.NSAutoreleasePool() )
            {
                try
                {
                    HttpWebRequest request = WebRequest.Create( m_sURL ) as HttpWebRequest;
                    request.Method = "POST";
                    request.ContentType = m_sContentType;
                    request.ContentLength = m_PostData.Length;

                    // Write the post data.
                    using ( Stream stream = request.GetRequestStream() )
                    {
                        stream.Write( m_PostData, 0, m_PostData.Length );
                        stream.Close();
                    }

                    System.Console.WriteLine( "Finished!" );

                    // We're done with the data now. Let it be garbage collected.
                    m_PostData = null;

                    // Finished!
                    m_PostStatus = AsyncHttpPostStatus.Success;
                }
                catch ( System.Exception e )
                {
                    System.Console.WriteLine( "Error in AsyncHttpPost.UploadThread:\n" + e.Message );
                    m_PostStatus = AsyncHttpPostStatus.Fail;
                }
            }
        }

        public AsyncHttpPostStatus PostStatus
        {
            get
            {
                return m_PostStatus;
            }
        }


        Thread m_UploadThread;

        // Queued to be handled in the main thread.
        byte [] m_PostData;

        AsyncHttpPostStatus m_PostStatus;
        string m_sContentType;
        string m_sURL;
    }
}

Answer 1

我认为您应该一次读入文件 1 KB（或任意大小）并将其写入 Web 请求。

类似这样的代码：

byte[] buffer = new buffer[1024];
int bytesRead = 0;
using (FileStream fileStream = File.OpenRead("YourFile.txt"))
{
    while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
    {
        httpPostStream.Write(buffer, 0, bytesRead);
    }
}

这超出了我的想象，但我认为这是正确的。

这样，当您确实不需要时，内存中就不会再有额外的 3MB 浮动空间。我认为这样的技巧在 iDevices（或其他设备）上比在桌面上更重要。

也测试缓冲区大小，更大的缓冲区会让你在一定程度上获得更好的速度（我记得 8KB 相当不错）。