Question

我有一个C＃项目，我必须访问处理器的当前工作负载，并确保在处理器的每个内核上运行一些特定的代码。我的问题是，访问我的处理器的工作负载似乎阻止我正确分配线程关联掩码。我在这里有一些代码，说明了问题：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Diagnostics;

namespace KernelAffinitySpike
{
    class Program
    {
        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern UIntPtr SetThreadAffinityMask(IntPtr hThread, UIntPtr dwThreadAffinityMask);

        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern IntPtr GetCurrentThread();

        private static PerformanceCounter cpuUsage;
        private static UIntPtr oldMask, newMask, testMask; // thread-level processor affinity masks.

        static void Main(string[] args)
        {
            InitPerformanceCounter();

            Console.WriteLine("Pre: thread affinity: " + CurrentThreadAffinityMask());
            if (AllKernelsAccessible())
                Console.WriteLine("Pre: all kernels accessible");
            else
            {
                Console.Write("Pre: some kernels not accessible: ");
                foreach (UInt32 kernel in InaccessibleKernels())
                    Console.Write(kernel + " ");
                Console.WriteLine();
            }

            float load = cpuUsage.NextValue();

            Console.WriteLine("Post: thread affinity: " + CurrentThreadAffinityMask());
            if (AllKernelsAccessible())
                Console.WriteLine("Post: all kernels accessible");
            else
            {
                Console.Write("Post: some kernels not accessible: ");
                foreach (UInt32 kernel in InaccessibleKernels())
                    Console.Write(kernel + " ");
                Console.WriteLine();
            }

            Console.ReadLine();
        }

        static void InitPerformanceCounter()
        {
            cpuUsage = new PerformanceCounter();
            cpuUsage.CategoryName = "Processor";
            cpuUsage.CounterName = "% Processor Time"; 
            cpuUsage.InstanceName = "_Total";
        }

        static UInt32 CurrentThreadAffinityMask()
        {
            oldMask = SetThreadAffinityMask(GetCurrentThread(), (UIntPtr) 3); // 3 just enables all processors on a dual core. I'm only interested in the return value.
            SetThreadAffinityMask(GetCurrentThread(), oldMask);
            return (UInt32) oldMask;
        }

        static List<UInt32> InaccessibleKernels()
        {
            List<UInt32> inaccessible = new List<UInt32>();
            for (int i = 0; i < Environment.ProcessorCount; i++)
            {
                newMask = (UIntPtr)(1 << i);
                oldMask = SetThreadAffinityMask(GetCurrentThread(), newMask);
                testMask = SetThreadAffinityMask(GetCurrentThread(), oldMask);
                if (newMask != testMask)
                    inaccessible.Add((UInt32) newMask);
            }
            return inaccessible;
        }

        static bool AllKernelsAccessible()
        {
            return InaccessibleKernels().Count == 0;
        }
    }
}

运行此代码会产生以下输出：

Pre: thread affinity: 3
Pre: all kernels accessible
Post: thread affinity: 2
Post: some kernels not accessible: 1

因此，似乎cpuUsage.NextValue调用以某种方式更改了线程关联掩码，并且还使得无法将掩码更改为1.确实有意义的是，Nextvalue调用必须与线程关联掩码进行交互在某种程度上，如果它是从每个内核聚合一个性能计数，但我无法理解，为什么它应该影响以后对线程关联掩码的更改。有没有人对此问题有解释或解决方法？

Answer 1

这是some other guy with same problem

似乎是微软未解决的问题。

以下是问题陈述 - 性能计数器更改线程的亲和力。 Microsoft support

他们建议调用SetThreadAffinity。）显然，他们的解决方案不起作用。

为什么NextValue调用performanceCounter会更改线程关联掩码

1 个答案: