ThreadPool: added PinWorkerThread helper function

Author: TheMostDiligent

Common/interface/ThreadPool.hpp

@@ -62,6 +62,18 @@ struct ThreadPoolCreateInfo
 
 RefCntAutoPtr<IThreadPool> CreateThreadPool(const ThreadPoolCreateInfo& ThreadPoolCI);
 
+/// Pins the worker thread to one of the allowed cores.
+///
+/// \param ThreadId         - The thread ID.
+/// \param AllowedCoresMask - The bit mask of allowed cores.
+/// \return                 - Previous thread affinity mask, or 0 if the function failed.
+///
+/// \remarks    The function selects the core by looping through the bits in the AllowedCoresMask.
+///             For example, if cores 1, 3, 6 are allowed by the mask, the threads will be assigned
+///             to cores 1, 3, 6, 1, 3, 6, etc.
+///
+///             This function can be used as the OnThreadStarted callback in the ThreadPoolCreateInfo.
+Uint64 PinWorkerThread(Uint32 ThreadId, Uint64 AllowedCoresMask);
 
 /// Base implementation of the IAsyncTask interface.
 class AsyncTaskBase : public ObjectBase<IAsyncTask>

Common/src/ThreadPool.cpp

@@ -34,6 +34,8 @@
 #include <condition_variable>
 #include <cfloat>
 
+#include "PlatformMisc.hpp"
+
 namespace Diligent
 {
 
@@ -350,4 +352,47 @@ RefCntAutoPtr<IThreadPool> CreateThreadPool(const ThreadPoolCreateInfo& ThreadPo
     return RefCntAutoPtr<ThreadPoolImpl>{MakeNewRCObj<ThreadPoolImpl>()(ThreadPoolCI)};
 }
 
+Uint64 PinWorkerThread(Uint32 ThreadId, Uint64 AllowedCoresMask)
+{
+    if (AllowedCoresMask == 0)
+    {
+        return 0;
+    }
+
+    Uint64 NumCores = std::thread::hardware_concurrency();
+    if (NumCores <= 1)
+        return 0;
+
+    Uint64 AffinityMask = AllowedCoresMask;
+    if (NumCores < 64)
+        AffinityMask &= (Uint64{1} << NumCores) - Uint64{1};
+
+    if (AffinityMask == 0)
+    {
+        LOG_WARNING_MESSAGE("Allowed cores mask (0x", std::hex, AllowedCoresMask, ") does not set any bits corresponding to ", std::dec, NumCores, " available cores");
+        return 0;
+    }
+
+    const Uint32 NumAllowedCores = PlatformMisc::CountOneBits(AffinityMask);
+    const Uint32 CoreBitInd      = ThreadId % NumAllowedCores;
+
+    for (Uint32 bit = 0; bit < CoreBitInd; ++bit)
+    {
+        VERIFY_EXPR(AffinityMask != 0);
+        Uint64 LSB = PlatformMisc::GetLSB(AffinityMask);
+        AffinityMask &= ~(Uint64{1} << LSB);
+    }
+
+    VERIFY_EXPR(AffinityMask != 0);
+    Uint32 WorkerCore = PlatformMisc::GetLSB(AffinityMask);
+    VERIFY_EXPR(WorkerCore < NumCores);
+    Uint64 PrevMask = PlatformMisc::SetCurrentThreadAffinity(Uint64{1} << WorkerCore) != 0;
+    if (PrevMask == 0)
+    {
+        LOG_WARNING_MESSAGE("Failed to pin worker thread ", ThreadId, " to core ", WorkerCore);
+    }
+
+    return PrevMask;
+}
+
 } // namespace Diligent

Platforms/Basic/interface/BasicPlatformMisc.hpp

@@ -1,5 +1,5 @@
 /*
- *  Copyright 2019-2022 Diligent Graphics LLC
+ *  Copyright 2019-2024 Diligent Graphics LLC
  *  Copyright 2015-2019 Egor Yusov
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
@@ -107,6 +107,9 @@ struct BasicPlatformMisc
     /// On failure, returns ThreadPriority::Unknown.
     static ThreadPriority SetCurrentThreadPriority(ThreadPriority Priority);
 
+    /// Sets the current thread affinity mask and on success returns the previous mask.
+    static Uint64 SetCurrentThreadAffinity(Uint64 Mask);
+
 private:
     static void SwapBytes16(Uint16& Val)
     {

Platforms/Basic/src/BasicPlatformMisc.cpp

@@ -1,5 +1,5 @@
 /*
- *  Copyright 2019-2022 Diligent Graphics LLC
+ *  Copyright 2019-2024 Diligent Graphics LLC
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
@@ -42,4 +42,10 @@ ThreadPriority BasicPlatformMisc::SetCurrentThreadPriority(ThreadPriority Priori
     return ThreadPriority::Unknown;
 }
 
+Uint64 BasicPlatformMisc::SetCurrentThreadAffinity(Uint64 Mask)
+{
+    LOG_WARNING_MESSAGE_ONCE("SetCurrentThreadAffinity is not implemented on this platform.");
+    return 0;
+}
+
 } // namespace Diligent

Platforms/Win32/src/Win32PlatformMisc.cpp

@@ -1,5 +1,5 @@
 /*
- *  Copyright 2019-2022 Diligent Graphics LLC
+ *  Copyright 2019-2024 Diligent Graphics LLC
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
@@ -35,8 +35,12 @@ namespace Diligent
 
 Uint64 WindowsMisc::SetCurrentThreadAffinity(Uint64 Mask)
 {
+#if PLATFORM_WIN32
     const auto hCurrThread = GetCurrentThread();
     return SetThreadAffinityMask(hCurrThread, static_cast<DWORD_PTR>(Mask));
+#else
+    return BasicPlatformMisc::SetCurrentThreadAffinity(Mask);
+#endif
 }