什么可能导致进行HttpWebRequest调用的巨大开销？

Question

当我使用小块中的HttpWebRequest(在Silverlight上)发送/接收数据时,我通过"localhost"连接测量500字节/秒的非常小的吞吐量.当以大块发送数据时,我得到2 MB/s,这快了5000倍.

有谁知道什么可能导致这个令人难以置信的巨大开销？

附加信息:

• 我正在使用HTTP POST方法
• 我在Firefox 3.6和Internet Explorer 7上都进行了性能测量.两者都显示了类似的结果.
• 我的CPU只加载了10%(四核,实际上是40%)
• WebClient显示了类似的结果
• WCF/SOAP显示了类似的结果

更新:我使用的Silverlight客户端代码本质上是我自己的WebClient类实现.我写它的原因是因为我注意到WebClient存在相同的性能问题,我认为HttpWebRequest可以调整性能问题.遗憾的是,这没有用.实施如下:

public class HttpCommChannel
{
    public delegate void ResponseArrivedCallback(object requestContext, BinaryDataBuffer response);

    public HttpCommChannel(ResponseArrivedCallback responseArrivedCallback)
    {
        this.responseArrivedCallback = responseArrivedCallback;
        this.requestSentEvent = new ManualResetEvent(false);
        this.responseArrivedEvent = new ManualResetEvent(true);
    }

    public void MakeRequest(object requestContext, string url, BinaryDataBuffer requestPacket)
    {
        responseArrivedEvent.WaitOne();
        responseArrivedEvent.Reset();

        this.requestMsg = requestPacket;
        this.requestContext = requestContext;

        this.webRequest = WebRequest.Create(url) as HttpWebRequest;
        this.webRequest.AllowReadStreamBuffering = true;
        this.webRequest.ContentType = "text/plain";
        this.webRequest.Method = "POST";

        this.webRequest.BeginGetRequestStream(new AsyncCallback(this.GetRequestStreamCallback), null);
        this.requestSentEvent.WaitOne();
    }

    void GetRequestStreamCallback(IAsyncResult asynchronousResult)
    {
        System.IO.Stream postStream = webRequest.EndGetRequestStream(asynchronousResult);

        postStream.Write(requestMsg.Data, 0, (int)requestMsg.Size);
        postStream.Close();

        requestSentEvent.Set();
        webRequest.BeginGetResponse(new AsyncCallback(this.GetResponseCallback), null);
    }

    void GetResponseCallback(IAsyncResult asynchronousResult)
    {
        HttpWebResponse response = (HttpWebResponse)webRequest.EndGetResponse(asynchronousResult);
        Stream streamResponse = response.GetResponseStream();
        Dim.Ensure(streamResponse.CanRead);
        byte[] readData = new byte[streamResponse.Length];
        Dim.Ensure(streamResponse.Read(readData, 0, (int)streamResponse.Length) == streamResponse.Length);
        streamResponse.Close();
        response.Close();

        webRequest = null;
        responseArrivedEvent.Set();
        responseArrivedCallback(requestContext, new BinaryDataBuffer(readData));
    }

    HttpWebRequest webRequest;
    ManualResetEvent requestSentEvent;
    BinaryDataBuffer requestMsg;
    object requestContext;
    ManualResetEvent responseArrivedEvent;
    ResponseArrivedCallback responseArrivedCallback;
}

我使用此代码来回传输数据到HTTP服务器.

更新:经过广泛的研究,我得出结论,性能问题是Silverlight v3所固有的.

Answer 1

您很可能正在见证 Nagle 算法的效果，请尝试：

this.webRequest.UseNagleAlgorithm.ServicePoint = false;

此外，Expect100Continue“握手”与 SOAP 服务调用性能相关：

this.webRequest.Expect100Continue.ServicePoint = false;

UDP日期：

刚刚意识到 ServicePoint 在 Compact Framework 中不可用。但是，您可以通过执行以下操作来证明这一点：

ServicePointManager.UseNagleAlgorithm = false

或者更改应用程序配置文件中的相关设置，或者 silverlight 中的任何等效设置？