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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / Scheduling / Scheduling.cs / 1305376 / Scheduling.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // Scheduling.cs // //[....] // // Infrastructure for setting up concurrent work, marshaling exceptions, determining // the recommended degree-of-parallelism, and so forth. // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System; using System.Collections.Generic; using System.Globalization; using System.Runtime.InteropServices; using System.Threading; using System.Diagnostics.Contracts; using System.Threading.Tasks; using System.Security; using System.Security.Permissions; namespace System.Linq.Parallel { //------------------------------------------------------------------------------------ // A simple helper class that offers common task scheduling functionality. // internal static class Scheduling { // Whether to preserve order by default, when neither AsOrdered nor AsUnordered is used. internal const bool DefaultPreserveOrder = false; // The default degree of parallelism, or -1 if unspecified. Dev unit tests set this value // to change the default DOP. internal static int DefaultDegreeOfParallelism = Math.Min(Environment.ProcessorCount, MAX_SUPPORTED_DOP); // The size to use for bounded buffers. @ internal const int DEFAULT_BOUNDED_BUFFER_CAPACITY = 512; // The number of bytes we want "chunks" to be, when partitioning, etc. We choose 4 cache // lines worth, assuming 128b cache line. Most (popular) architectures use 64b cache lines, // but choosing 128b works for 64b too whereas a multiple of 64b isn't necessarily sufficient // for 128b cache systems. So 128b it is. internal const int DEFAULT_BYTES_PER_CHUNK = 128 * 4; // The number of milliseconds before we assume a producer has been zombied. // @ internal const int ZOMBIED_PRODUCER_TIMEOUT = Timeout.Infinite; // The largest number of partitions that PLINQ supports. internal const int MAX_SUPPORTED_DOP = 63; //----------------------------------------------------------------------------------- // Calculates the proper amount of DOP. This takes into consideration dynamic nesting. // internal static int GetDefaultDegreeOfParallelism() { return DefaultDegreeOfParallelism; } //----------------------------------------------------------------------------------- // Gets the recommended "chunk size" for a particular CLR type. // // Notes: // We try to recommend some reasonable "chunk size" for the data, but this is // clearly a tradeoff, and requires a bit of experimentation. A larger chunk size // can help locality, but if it's too big we may end up either stalling another // partition (if enumerators are calculating data on demand) or skewing the // distribution of data among the partitions. // internal static int GetDefaultChunkSize() { int chunkSize; if (typeof(T).IsValueType) { // @ if (typeof(T).StructLayoutAttribute.Value == LayoutKind.Explicit) { chunkSize = Math.Max(1, DEFAULT_BYTES_PER_CHUNK / Marshal.SizeOf(typeof(T))); } else { // We choose '128' because this ensures, no matter the actual size of the value type, // the total bytes used will be a multiple of 128. This ensures it's cache aligned. chunkSize = 128; } } else { Contract.Assert((DEFAULT_BYTES_PER_CHUNK % IntPtr.Size) == 0, "bytes per chunk should be a multiple of pointer size"); chunkSize = (DEFAULT_BYTES_PER_CHUNK / IntPtr.Size); } TraceHelpers.TraceInfo("Scheduling::GetDefaultChunkSize({0}) -- returning {1}", typeof(T), chunkSize); return chunkSize; } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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