C#WPF应用程序使用太多内存而GC.GetTotalMemory()为低

Question

我写了两个线程的WPF应用程序 - 主线程是GUI线程,另一个线程是worker.
App有一个带有一些控件的WPF表单.有一个按钮,允许选择目录.选择目录后,应用程序将扫描该目录中的.jpg文件,并检查其缩略图是否在哈希表中.如果他们是,它什么都不做.否则它将他们的完整文件名添加到工作队列.
Worker正在从这个队列中获取文件名,加载JPEG图像(使用WPF的JpegBitmapDecoder和BitmapFrame),制作它们的缩略图(使用WPF的TransformedBitmap)并将它们添加到哈希表中.
一切正常,除了这个应用程序在为大图像(如5000x5000像素)制作缩略图时的内存消耗.我在表单上添加了文本框以显示内存消耗(GC.GetTotalMemory()和Process.GetCurrentProcess().PrivateMemorySize64)并且非常惊讶,因为GC.GetTotalMemory()保持接近1-2 MB,而私有内存大小不断增长,特别是在加载新图像时(每张图像约+ 100Mb).
即使在加载所有图像,制作它们的缩略图并释放原始图像之后,私有内存大小仍保持在~700-800Mbytes.我的VirtualBox仅限于512Mb的物理内存,VirtualBox中的Windows开始交换很多来处理这种巨大的内存消耗.我想我做错了什么,但我不知道如何调查这个问题,因为根据GC,分配的内存大小非常低.

附加缩略图加载器类的代码:

class ThumbnailLoader
{
    Hashtable thumbnails;
    Queue<string> taskqueue;
    EventWaitHandle wh;
    Thread[] workers;
    bool stop;
    object locker;
    int width, height, processed, added;

    public ThumbnailLoader()
    {
        int workercount,i;
        wh = new AutoResetEvent(false);
        thumbnails = new Hashtable();
        taskqueue = new Queue<string>();
        stop = false;
        locker = new object();
        width = height = 64;
        processed = added = 0;
        workercount = Environment.ProcessorCount;
        workers=new Thread[workercount];
        for (i = 0; i < workercount; i++) {
            workers[i] = new Thread(Worker);
            workers[i].IsBackground = true;
            workers[i].Priority = ThreadPriority.Highest;
            workers[i].Start();
        }
    }

    public void SetThumbnailSize(int twidth, int theight)
    {
        width = twidth;
        height = theight;
        if (thumbnails.Count!=0) AddTask("#resethash");
    }

    public void GetProgress(out int Added, out int Processed)
    {
        Added = added;
        Processed = processed;
    }

    private void AddTask(string filename)
    {
        lock(locker) {
            taskqueue.Enqueue(filename);
            wh.Set();
            added++;
        }
    }

    private string NextTask()
    {
        lock(locker) {
            if (taskqueue.Count == 0) return null;
            else {
                processed++;
                return taskqueue.Dequeue();
            }
        }
    }

    public static string FileNameToHash(string s)
    {
        return FormsAuthentication.HashPasswordForStoringInConfigFile(s, "MD5");
    }

    public bool GetThumbnail(string filename,out BitmapFrame thumbnail)
    {
        string hash;
        hash = FileNameToHash(filename);
        if (thumbnails.ContainsKey(hash)) {
            thumbnail=(BitmapFrame)thumbnails[hash];
            return true;
        }
        AddTask(filename);
        thumbnail = null;
        return false;
    }

    private BitmapFrame LoadThumbnail(string filename)
    {
        FileStream fs;
        JpegBitmapDecoder bd;
        BitmapFrame oldbf, bf;
        TransformedBitmap tb;
        double scale, dx, dy;
        fs = new FileStream(filename, FileMode.Open);
        bd = new JpegBitmapDecoder(fs, BitmapCreateOptions.None, BitmapCacheOption.OnLoad);
        oldbf = bd.Frames[0];
        dx = (double)oldbf.Width / width;
        dy = (double)oldbf.Height / height;
        if (dx > dy) scale = 1 / dx;
        else scale = 1 / dy;
        tb = new TransformedBitmap(oldbf, new ScaleTransform(scale, scale));
        bf = BitmapFrame.Create(tb);
        fs.Close();
        oldbf = null;
        bd = null;
        GC.Collect();
        return bf;
    }

    public void Dispose()
    {
        lock(locker) {
            stop = true;
        }
        AddTask(null);
        foreach (Thread worker in workers) {
            worker.Join();
        }
        wh.Close();
    }

    private void Worker()
    {
        string curtask,hash;
        while (!stop) {
            curtask = NextTask();
            if (curtask == null) wh.WaitOne();
            else {
                if (curtask == "#resethash") thumbnails.Clear();
                else {
                    hash = FileNameToHash(curtask);
                    try {
                        thumbnails[hash] = LoadThumbnail(curtask);
                    }
                    catch {
                        thumbnails[hash] = null;
                    }
                }
            }
        }
    }
}

Answer 1

我怀疑BitmapCacheOption.OnLoad是将图像添加到Framework的内存占用空间,但由于您不拥有图像缓存中的对象,因此它们不会出现在GC方法调用的结果中.尝试使用BitmapCacheOption.None,看看是否能解决你的记忆问题.注意:这样做会对性能产生巨大影响.