Scheduling.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ 4.0 / 4.0 / 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.
// ==++== 
//
//   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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