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POHow to prevent saving the same file multiple times in the memory
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  1. POHow to prevent saving the same file multiple times in the memory
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    copied!<p>i want to read files (1 gb) per byte by using MemoryMappedFile from couple of threads (and processes ! ), my example code:</p> <pre><code>static unsafe void T() { MemoryMappedFile mmf = null; var mmfName = "q1"; var fname = @"%file_name%"; lock (Lock) { try { mmf = MemoryMappedFile.OpenExisting(mmfName, MemoryMappedFileRights.Read, HandleInheritability.Inheritable); Console.WriteLine("ok - open"); } catch { FileStream fs = null; try { fs = new FileStream(fname, System.IO.FileMode.Open, FileAccess.Read, FileShare.Read, 4 * 1024, true); mmf = MemoryMappedFile.CreateFromFile(fs, mmfName, 0, MemoryMappedFileAccess.Read, null, HandleInheritability.Inheritable, false); Console.WriteLine("ok - load"); } catch { Console.WriteLine("fail"); } } } var size = new System.IO.FileInfo(fname).Length; byte* ptr = (byte*)0; var vh = mmf.CreateViewAccessor(0, 0, MemoryMappedFileAccess.Read).SafeMemoryMappedViewHandle; vh.AcquirePointer(ref ptr); var rnd = new Random(); for (int i = 0; i &lt; size; i++) { var t = *(ptr + (int)rnd.Next(0, (int)size)); } } </code></pre> <p>and code to run the test:</p> <pre><code> static unsafe void Main(string[] args) { Parallel.Invoke(T, T, T); Console.WriteLine("done"); Console.ReadLine(); } </code></pre> <p>app output:</p> <pre><code>ok - load ok - open ok - open </code></pre> <p>The problem that my app takes 3 gb in memory (working set). So it copies file 3 times in memory. I want only one copy in memory (1 gb) for "ok - load" thread, and no copies for reading ("ok - open") threads.</p> <p>Any ideas? (c#, 4.5, vs12, win7)</p> <p>Thanks for help </p>
 

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