[OpenMP] Move memory manager to plugin and make it a common interface

[tianshilei1992]

Summary

The lifetime of libomptarget and its opened plugins are not aligned
and it's hard for libomptarget to determine when the plugins are destroyed.
As a result, some issues (see D94256 for details) occur on some platforms.
Actually, if we take target memory as target resources, same as other resources,
such as CUDA streams, in each plugin, then the memory manager should also be in
the plugin. Also considering some platforms may want to opt out the feature, it
makes sense to move the memory manager to plugin, make it a common interface, and
let plguin developers determine whether they need it. This is what this patch does.
CUDA plugin is taken as example to show how to integrate it. In this way, we can
also get a bonus that different thresholds can be set for different platforms.

[jdoerfert]

This looks better.

We could make an interface, let memory manager and DeviceAllocatorTy implement it, and simply fill the "allocator list" with the appropriate ones. Unsure if that is preferable over the if(UseMemoryManager) conditional but it might be nicer to read.

Update the docs wrt. environment vars, and also look for the generic LIBOMPTARGET_MEMORY_MANAGER_THRESHOLD. Or only look for that one.

openmp/libomptarget/plugins/cuda/src/rtl.cpp

456

Don't we always need to create the device allocators?

464

No need for the if.

[tianshilei1992]

openmp/libomptarget/plugins/cuda/src/rtl.cpp

456

Oh, yeah. Will fix that.

[tianshilei1992]

Use interface class to replace the template

[tianshilei1992]

Still uses LIBOMPTARGET_MEMORY_MANAGER_THRESHOLD. A plugin can extends the function getSizeThresholdFromEnv in the future to make separate control.

[JonChesterfield]

That's much nicer, thank you. I wouldn't have thought of using inheritance here and like how it's turned out.

[jdoerfert]

openmp/libomptarget/plugins/common/MemoryManager.h

97

As clang tidy tells you, this can be problematic. Easy way out of this is to move the helpers as static functions into the memory manager, especially given that they look at MEMORY_MANAGER env vars.

115

Given tat you have the DeviceAllocatorTy already, why not inherit here and in the cuda class?

280

Nit: No need for the ifdef, I think. Given all the other DP macros around anyway. also other places.

openmp/libomptarget/plugins/cuda/src/rtl.cpp

28

common should be in the include path via cmake.

[jdoerfert]

I forgot to submit some nits yesterday, address what makes sense ^. LGTM

[tianshilei1992]

Fixed some comments

[tianshilei1992]

Fixed header guard

openmp/libomptarget/plugins/common/MemoryManager.h

+//===----------- MemoryManager.h - Target independent memory manager ------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Target independent memory manager.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_OPENMP_LIBOMPTARGET_PLUGINS_COMMON_MEMORYMANAGER_H
+#define LLVM_OPENMP_LIBOMPTARGET_PLUGINS_COMMON_MEMORYMANAGER_H
+
+#include <cassert>
+#include <functional>
+#include <list>
+#include <mutex>
+#include <set>
+#include <unordered_map>
+#include <vector>
+
+#include "Debug.h"
+#include "omptargetplugin.h"
+
+namespace {
+constexpr const size_t BucketSize[] = {
+    0,       1U << 2, 1U << 3,  1U << 4,  1U << 5,  1U << 6, 1U << 7,
+    1U << 8, 1U << 9, 1U << 10, 1U << 11, 1U << 12, 1U << 13};
+
+constexpr const int NumBuckets = sizeof(BucketSize) / sizeof(BucketSize[0]);
+
+/// The threshold to manage memory using memory manager. If the request size is
+/// larger than \p SizeThreshold, the allocation will not be managed by the
+/// memory manager. This variable can be configured via an env \p
+/// LIBOMPTARGET_MEMORY_MANAGER_THRESHOLD. By default, the value is 8KB.
+size_t SizeThreshold = 1U << 13;
+
+/// Find the previous number that is power of 2 given a number that is not power
+/// of 2.
+size_t floorToPowerOfTwo(size_t Num) {
+  Num |= Num >> 1;
+  Num |= Num >> 2;
+  Num |= Num >> 4;
+  Num |= Num >> 8;
+  Num |= Num >> 16;
+#if INTPTR_MAX == INT64_MAX
+  Num |= Num >> 32;
+#elif INTPTR_MAX == INT32_MAX
+  // Do nothing with 32-bit
+#else
+#error Unsupported architecture
+#endif
+  Num += 1;
+  return Num >> 1;
+}
+
+/// Find a suitable bucket
+int findBucket(size_t Size) {
+  const size_t F = floorToPowerOfTwo(Size);
+
+  DP("findBucket: Size %zu is floored to %zu.\n", Size, F);
+
+  int L = 0, H = NumBuckets - 1;
+  while (H - L > 1) {
+    int M = (L + H) >> 1;
+    if (BucketSize[M] == F)
+      return M;
+    if (BucketSize[M] > F)
+      H = M - 1;
+    else
+      L = M;
+  }
+
+  assert(L >= 0 && L < NumBuckets && "L is out of range");
+
+  DP("findBucket: Size %zu goes to bucket %d\n", Size, L);
+
+  return L;
+}
+} // namespace
+
+/// Class of memory manager. The template type \p DeviceAllocatorTy should be
+/// implemented by plugin developers to support target memory allocation and
+/// free. It must support the following two interfaces:
+/// - void *DeviceAllocatorTy::allocate(size_t Size, void *HstPtr)
+/// - int DeviceAllocatorTy::free(void *TgtPtr)
+/// The memory manager is per-device by using per-device allocator. Therefore,
+/// each plugin using memory manager should have an allocator for each device.
+template <typename DeviceAllocatorTy> class MemoryManagerTy {
+  /// A structure stores the meta data of a target pointer
+  struct NodeTy {
+    /// Memory size
+    const size_t Size;
+    /// Target pointer
+    void *Ptr;
+
+    /// Constructor
+    NodeTy(size_t Size, void *Ptr) : Size(Size), Ptr(Ptr) {}
+  };
+
+  /// To make \p NodePtrTy ordered when they're put into \p std::multiset.
+  struct NodeCmpTy {
+    bool operator()(const NodeTy &LHS, const NodeTy &RHS) const {
+      return LHS.Size < RHS.Size;
+    }
+  };
+
+  /// A \p FreeList is a set of Nodes. We're using \p std::multiset here to make
+  /// the look up procedure more efficient.
+  using FreeListTy = std::multiset<std::reference_wrapper<NodeTy>, NodeCmpTy>;
+
+  /// A list of \p FreeListTy entries, each of which is a \p std::multiset of
+  /// Nodes whose size is less or equal to a specific bucket size.
+  std::vector<FreeListTy> FreeLists;
+  /// A list of mutex for each \p FreeListTy entry
+  std::vector<std::mutex> FreeListLocks;
+  /// A table to map from a target pointer to its node
+  std::unordered_map<void *, NodeTy> PtrToNodeTable;
+  /// The mutex for the table \p PtrToNodeTable
+  std::mutex MapTableLock;
+
+  /// The reference to a device allocator
+  DeviceAllocatorTy &DeviceAllocator;
+
+  /// Request memory from target device
+  void *allocateOnDevice(size_t Size, void *HstPtr) const {
+    return DeviceAllocator.allocate(Size, HstPtr);
+  }
+
+  /// Deallocate data on device
+  int deleteOnDevice(void *Ptr) const { return DeviceAllocator.free(Ptr); }
+
+  /// This function is called when it tries to allocate memory on device but the
+  /// device returns out of memory. It will first free all memory in the
+  /// FreeList and try to allocate again.
+  void *freeAndAllocate(size_t Size, void *HstPtr) {
+    std::vector<void *> RemoveList;
+
+    // Deallocate all memory in FreeList
+    for (int I = 0; I < NumBuckets; ++I) {
+      FreeListTy &List = FreeLists[I];
+      std::lock_guard<std::mutex> Lock(FreeListLocks[I]);
+      if (List.empty())
+        continue;
+      for (const NodeTy &N : List) {
+        deleteOnDevice(N.Ptr);
+        RemoveList.push_back(N.Ptr);
+      }
+      FreeLists[I].clear();
+    }
+
+    // Remove all nodes in the map table which have been released
+    if (!RemoveList.empty()) {
+      std::lock_guard<std::mutex> LG(MapTableLock);
+      for (void *P : RemoveList)
+        PtrToNodeTable.erase(P);
+    }
+
+    // Try allocate memory again
+    return allocateOnDevice(Size, HstPtr);
+  }
+
+  /// The goal is to allocate memory on the device. It first tries to
+  /// allocate directly on the device. If a \p nullptr is returned, it might
+  /// be because the device is OOM. In that case, it will free all unused
+  /// memory and then try again.
+  void *allocateOrFreeAndAllocateOnDevice(size_t Size, void *HstPtr) {
+    void *TgtPtr = allocateOnDevice(Size, HstPtr);
+    // We cannot get memory from the device. It might be due to OOM. Let's
+    // free all memory in FreeLists and try again.
+    if (TgtPtr == nullptr) {
+      DP("Failed to get memory on device. Free all memory in FreeLists and "
+         "try again.\n");
+      TgtPtr = freeAndAllocate(Size, HstPtr);
+    }
+
+#ifdef OMPTARGET_DEBUG
+    if (TgtPtr == nullptr)
+      DP("Still cannot get memory on device probably because the device is "
+         "OOM.\n");
+#endif
+
+    return TgtPtr;
+  }
+
+public:
+  /// Constructor. If \p Threshold is non-zero, then the default threshold will
+  /// be overwritten by \p Threshold.
+  MemoryManagerTy(DeviceAllocatorTy &DeviceAllocator, size_t Threshold = 0)
+      : FreeLists(NumBuckets), FreeListLocks(NumBuckets),
+        DeviceAllocator(DeviceAllocator) {
+    if (Threshold)
+      SizeThreshold = Threshold;
+  }
+
+  /// Destructor
+  ~MemoryManagerTy() {
+    for (auto Itr = PtrToNodeTable.begin(); Itr != PtrToNodeTable.end();
+         ++Itr) {
+      assert(Itr->second.Ptr && "nullptr in map table");
+      deleteOnDevice(Itr->second.Ptr);
+    }
+  }
+
+  /// Allocate memory of size \p Size from target device. \p HstPtr is used to
+  /// assist the allocation.
+  void *allocate(size_t Size, void *HstPtr) {
+    // If the size is zero, we will not bother the target device. Just return
+    // nullptr directly.
+    if (Size == 0)
+      return nullptr;
+
+    DP("MemoryManagerTy::allocate: size %zu with host pointer " DPxMOD ".\n",
+       Size, DPxPTR(HstPtr));
+
+    // If the size is greater than the threshold, allocate it directly from
+    // device.
+    if (Size > SizeThreshold) {
+      DP("%zu is greater than the threshold %zu. Allocate it directly from "
+         "device\n",
+         Size, SizeThreshold);
+      void *TgtPtr = allocateOrFreeAndAllocateOnDevice(Size, HstPtr);
+
+      DP("Got target pointer " DPxMOD ". Return directly.\n", DPxPTR(TgtPtr));
+
+      return TgtPtr;
+    }
+
+    NodeTy *NodePtr = nullptr;
+
+    // Try to get a node from FreeList
+    {
+      const int B = findBucket(Size);
+      FreeListTy &List = FreeLists[B];
+
+      NodeTy TempNode(Size, nullptr);
+      std::lock_guard<std::mutex> LG(FreeListLocks[B]);
+      const auto Itr = List.find(TempNode);
+
+      if (Itr != List.end()) {
+        NodePtr = &Itr->get();
+        List.erase(Itr);
+      }
+    }
+
+#ifdef OMPTARGET_DEBUG
+    if (NodePtr != nullptr)
+      DP("Find one node " DPxMOD " in the bucket.\n", DPxPTR(NodePtr));
+#endif
+
+    // We cannot find a valid node in FreeLists. Let's allocate on device and
+    // create a node for it.
+    if (NodePtr == nullptr) {
+      DP("Cannot find a node in the FreeLists. Allocate on device.\n");
+      // Allocate one on device
+      void *TgtPtr = allocateOrFreeAndAllocateOnDevice(Size, HstPtr);
+
+      if (TgtPtr == nullptr)
+        return nullptr;
+
+      // Create a new node and add it into the map table
+      {
+        std::lock_guard<std::mutex> Guard(MapTableLock);
+        auto Itr = PtrToNodeTable.emplace(TgtPtr, NodeTy(Size, TgtPtr));
+        NodePtr = &Itr.first->second;
+      }
+
+      DP("Node address " DPxMOD ", target pointer " DPxMOD ", size %zu\n",
+         DPxPTR(NodePtr), DPxPTR(TgtPtr), Size);
+    }
+
+    assert(NodePtr && "NodePtr should not be nullptr at this point");
+
+    return NodePtr->Ptr;
+  }
+
+  /// Deallocate memory pointed by \p TgtPtr
+  int free(void *TgtPtr) {
+    DP("MemoryManagerTy::free: target memory " DPxMOD ".\n", DPxPTR(TgtPtr));
+
+    NodeTy *P = nullptr;
+
+    // Look it up into the table
+    {
+      std::lock_guard<std::mutex> G(MapTableLock);
+      auto Itr = PtrToNodeTable.find(TgtPtr);
+
+      // We don't remove the node from the map table because the map does not
+      // change.
+      if (Itr != PtrToNodeTable.end())
+        P = &Itr->second;
+    }
+
+    // The memory is not managed by the manager
+    if (P == nullptr) {
+      DP("Cannot find its node. Delete it on device directly.\n");
+      return deleteOnDevice(TgtPtr);
+    }
+
+    // Insert the node to the free list
+    const int B = findBucket(P->Size);
+
+    DP("Found its node " DPxMOD ". Insert it to bucket %d.\n", DPxPTR(P), B);
+
+    {
+      std::lock_guard<std::mutex> G(FreeListLocks[B]);
+      FreeLists[B].insert(*P);
+    }
+
+    return OFFLOAD_SUCCESS;
+  }
+};
+
+#endif // LLVM_OPENMP_LIBOMPTARGET_PLUGINS_COMMON_MEMORYMANAGER_H

openmp/libomptarget/plugins/cuda/src/rtl.cpp

 //===----RTLs/cuda/src/rtl.cpp - Target RTLs Implementation ------- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // RTL for CUDA machine
 //
 //===----------------------------------------------------------------------===//
 
 #include <cassert>
 #include <cstddef>
 #include <cuda.h>
 #include <list>
 #include <memory>
 #include <mutex>
 #include <string>
 #include <vector>
 
 #include "Debug.h"
 #include "omptargetplugin.h"
 
 #define TARGET_NAME CUDA
 #define DEBUG_PREFIX "Target " GETNAME(TARGET_NAME) " RTL"
 
+#include "../../common/MemoryManager.h"
+
 // Utility for retrieving and printing CUDA error string.
 #ifdef OMPTARGET_DEBUG
 #define CUDA_ERR_STRING(err)                                                   \
   do {                                                                         \
     if (getDebugLevel() > 0) {                                                 \
       const char *errStr = nullptr;                                            \
       CUresult errStr_status = cuGetErrorString(err, &errStr);                 \
       if (errStr_status == CUDA_ERROR_INVALID_VALUE)                           \
class DeviceRTLTy {
   static constexpr const int HardThreadLimit = 1024;
   static constexpr const int DefaultNumTeams = 128;
   static constexpr const int DefaultNumThreads = 128;
 
   std::unique_ptr<StreamManagerTy> StreamManager;
   std::vector<DeviceDataTy> DeviceData;
   std::vector<CUmodule> Modules;
 
+  /// A class responsible for interacting with device native runtime library to
+  /// allocate and free memory.
+  class DeviceAllocatorTy {
+    const int DeviceId;
+    const std::vector<DeviceDataTy> &DeviceData;
+
+  public:
+    DeviceAllocatorTy(int DeviceId, std::vector<DeviceDataTy> &DeviceData)
+        : DeviceId(DeviceId), DeviceData(DeviceData) {}
+
+    void *allocate(size_t Size, void *) const {
+      if (Size == 0)
+        return nullptr;
+
+      CUresult Err = cuCtxSetCurrent(DeviceData[DeviceId].Context);
+      if (!checkResult(Err, "Error returned from cuCtxSetCurrent\n"))
+        return nullptr;
+
+      CUdeviceptr DevicePtr;
+      Err = cuMemAlloc(&DevicePtr, Size);
+      if (!checkResult(Err, "Error returned from cuMemAlloc\n"))
+        return nullptr;
+
+      return (void *)DevicePtr;
+    }
+
+    int free(void *TgtPtr) const {
+      CUresult Err = cuCtxSetCurrent(DeviceData[DeviceId].Context);
+      if (!checkResult(Err, "Error returned from cuCtxSetCurrent\n"))
+        return OFFLOAD_FAIL;
+
+      Err = cuMemFree((CUdeviceptr)TgtPtr);
+      if (!checkResult(Err, "Error returned from cuMemFree\n"))
+        return OFFLOAD_FAIL;
+
+      return OFFLOAD_SUCCESS;
+    }
+  };
+
+  /// A list of device allocators
+  std::vector<std::unique_ptr<DeviceAllocatorTy>> DeviceAllocators;
+
+  /// A vector of memory managers. Since the memory manager is non-copyable and
+  // non-removable, we wrap them into std::unique_ptr.
+  using CUDAMemoryManagerTy = MemoryManagerTy<DeviceAllocatorTy>;
+  std::vector<std::unique_ptr<CUDAMemoryManagerTy>> MemoryManagers;
+
+  /// Whether use memory manager
+  bool UseMemoryManager = true;
+
   // Record entry point associated with device
   void addOffloadEntry(const int DeviceId, const __tgt_offload_entry entry) {
     FuncOrGblEntryTy &E = DeviceData[DeviceId].FuncGblEntries.back();
     E.Entries.push_back(entry);
   }
 
   // Return a pointer to the entry associated with the pointer
   const __tgt_offload_entry *getOffloadEntry(const int DeviceId,
DeviceRTLTy()
     if (const char *EnvStr = getenv("OMP_NUM_TEAMS")) {
       // OMP_NUM_TEAMS has been set
       EnvNumTeams = std::stoi(EnvStr);
       DP("Parsed OMP_NUM_TEAMS=%d\n", EnvNumTeams);
     }
 
     StreamManager =
         std::make_unique<StreamManagerTy>(NumberOfDevices, DeviceData);
+
+    // If user set the env to 0, the memory manager will be disabled.
+    size_t MemoryManagerThreshold = 0;
+    if (const char *Env =
+            std::getenv("LIBOMPTARGET_NVPTX_MEMORY_MANAGER_THRESHOLD")) {
+      MemoryManagerThreshold = std::stoul(Env);
+      if (MemoryManagerThreshold == 0) {
+        DP("Disabled memory manager as user set "
+           "LIBOMPTARGET_NVPTX_MEMORY_MANAGER_THRESHOLD=0.\n");
+        UseMemoryManager = false;
+      }
+    }
+
+    // The two loops cannot be merged in case `DeviceAllocators.emplace_back`
+    // resize the vector so the reference to
+    if (UseMemoryManager) {
+      for (int I = 0; I < NumberOfDevices; ++I) {
+        DeviceAllocators.emplace_back(
+            std::make_unique<DeviceAllocatorTy>(I, DeviceData));
+        MemoryManagers.emplace_back(std::make_unique<CUDAMemoryManagerTy>(
+            *DeviceAllocators[I], MemoryManagerThreshold));
+      }
+    }
   }
 
   ~DeviceRTLTy() {
-    // First destruct stream manager in case of Contexts is destructed before it
+    // We first destruct memory managers in case that its dependent data are
+    // destroyed before it.
+    if (UseMemoryManager)
+      for (auto &M : MemoryManagers)
+        M.release();
+
     StreamManager = nullptr;
 
     for (CUmodule &M : Modules)
       // Close module
       if (M)
         checkResult(cuModuleUnload(M), "Error returned from cuModuleUnload\n");
 
     for (DeviceDataTy &D : DeviceData) {
#endif
            "environment setting.\n");
       }
     }
 
     return getOffloadEntriesTable(DeviceId);
   }
 
   void *dataAlloc(const int DeviceId, const int64_t Size) const {
-    if (Size == 0)
-      return nullptr;
+    if (UseMemoryManager)
+      return MemoryManagers[DeviceId]->allocate(Size, nullptr);
 
-    CUresult Err = cuCtxSetCurrent(DeviceData[DeviceId].Context);
-    if (!checkResult(Err, "Error returned from cuCtxSetCurrent\n"))
-      return nullptr;
-
-    CUdeviceptr DevicePtr;
-    Err = cuMemAlloc(&DevicePtr, Size);
-    if (!checkResult(Err, "Error returned from cuMemAlloc\n"))
-      return nullptr;
-
-    return (void *)DevicePtr;
+    return DeviceAllocators[DeviceId]->allocate(Size, nullptr);
   }
 
   int dataSubmit(const int DeviceId, const void *TgtPtr, const void *HstPtr,
                  const int64_t Size, __tgt_async_info *AsyncInfoPtr) const {
     assert(AsyncInfoPtr && "AsyncInfoPtr is nullptr");
 
     CUresult Err = cuCtxSetCurrent(DeviceData[DeviceId].Context);
     if (!checkResult(Err, "Error returned from cuCtxSetCurrent\n"))
if (SrcDevId != DstDevId) {
              DPxPTR(SrcPtr), SrcDevId, DPxPTR(DstPtr), DstDevId);
       CUDA_ERR_STRING(Err);
     }
 
     return memcpyDtoD(SrcPtr, DstPtr, Size, Stream);
   }
 
   int dataDelete(const int DeviceId, void *TgtPtr) const {
-    CUresult Err = cuCtxSetCurrent(DeviceData[DeviceId].Context);
-    if (!checkResult(Err, "Error returned from cuCtxSetCurrent\n"))
-      return OFFLOAD_FAIL;
+    if (UseMemoryManager)
+      return MemoryManagers[DeviceId]->free(TgtPtr);
 
-    Err = cuMemFree((CUdeviceptr)TgtPtr);
-    if (!checkResult(Err, "Error returned from cuMemFree\n"))
-      return OFFLOAD_FAIL;
-
-    return OFFLOAD_SUCCESS;
+    return DeviceAllocators[DeviceId]->free(TgtPtr);
   }
 
   int runTargetTeamRegion(const int DeviceId, void *TgtEntryPtr, void **TgtArgs,
                           ptrdiff_t *TgtOffsets, const int ArgNum,
                           const int TeamNum, const int ThreadLimit,
                           const unsigned int LoopTripCount,
                           __tgt_async_info *AsyncInfo) const {
     CUresult Err = cuCtxSetCurrent(DeviceData[DeviceId].Context);

openmp/libomptarget/src/CMakeLists.txt

 ##===----------------------------------------------------------------------===##
 
 libomptarget_say("Building offloading runtime library libomptarget.")
 
 set(LIBOMPTARGET_SRC_FILES
   ${CMAKE_CURRENT_SOURCE_DIR}/api.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/device.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/interface.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/MemoryManager.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/rtl.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/omptarget.cpp
 )
 
 include_directories(${LIBOMPTARGET_LLVM_MAIN_INCLUDE_DIR})
 
 # Build libomptarget library with libdl dependency. Add LLVMSupport
 # dependency if building in-tree with profiling enabled.

openmp/libomptarget/src/MemoryManager.h

-//===----------- MemoryManager.h - Target independent memory manager ------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// Declarations for target independent memory manager.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_OPENMP_LIBOMPTARGET_SRC_MEMORYMANAGER_H
-#define LLVM_OPENMP_LIBOMPTARGET_SRC_MEMORYMANAGER_H
-
-#include <cassert>
-#include <functional>
-#include <list>
-#include <mutex>
-#include <set>
-#include <unordered_map>
-#include <vector>
-
-// Forward declaration
-struct DeviceTy;
-
-class MemoryManagerTy {
-  /// A structure stores the meta data of a target pointer
-  struct NodeTy {
-    /// Memory size
-    const size_t Size;
-    /// Target pointer
-    void *Ptr;
-
-    /// Constructor
-    NodeTy(size_t Size, void *Ptr) : Size(Size), Ptr(Ptr) {}
-  };
-
-  /// To make \p NodePtrTy ordered when they're put into \p std::multiset.
-  struct NodeCmpTy {
-    bool operator()(const NodeTy &LHS, const NodeTy &RHS) const {
-      return LHS.Size < RHS.Size;
-    }
-  };
-
-  /// A \p FreeList is a set of Nodes. We're using \p std::multiset here to make
-  /// the look up procedure more efficient.
-  using FreeListTy = std::multiset<std::reference_wrapper<NodeTy>, NodeCmpTy>;
-
-  /// A list of \p FreeListTy entries, each of which is a \p std::multiset of
-  /// Nodes whose size is less or equal to a specific bucket size.
-  std::vector<FreeListTy> FreeLists;
-  /// A list of mutex for each \p FreeListTy entry
-  std::vector<std::mutex> FreeListLocks;
-  /// A table to map from a target pointer to its node
-  std::unordered_map<void *, NodeTy> PtrToNodeTable;
-  /// The mutex for the table \p PtrToNodeTable
-  std::mutex MapTableLock;
-  /// A reference to its corresponding \p DeviceTy object
-  DeviceTy &Device;
-
-  /// Request memory from target device
-  void *allocateOnDevice(size_t Size, void *HstPtr) const;
-
-  /// Deallocate data on device
-  int deleteOnDevice(void *Ptr) const;
-
-  /// This function is called when it tries to allocate memory on device but the
-  /// device returns out of memory. It will first free all memory in the
-  /// FreeList and try to allocate again.
-  void *freeAndAllocate(size_t Size, void *HstPtr);
-
-  /// The goal is to allocate memory on the device. It first tries to allocate
-  /// directly on the device. If a \p nullptr is returned, it might be because
-  /// the device is OOM. In that case, it will free all unused memory and then
-  /// try again.
-  void *allocateOrFreeAndAllocateOnDevice(size_t Size, void *HstPtr);
-
-public:
-  /// Constructor. If \p Threshold is non-zero, then the default threshold will
-  /// be overwritten by \p Threshold.
-  MemoryManagerTy(DeviceTy &Dev, size_t Threshold = 0);
-
-  /// Destructor
-  ~MemoryManagerTy();
-
-  /// Allocate memory of size \p Size from target device. \p HstPtr is used to
-  /// assist the allocation.
-  void *allocate(size_t Size, void *HstPtr);
-
-  /// Deallocate memory pointed by \p TgtPtr
-  int free(void *TgtPtr);
-};
-
-#endif // LLVM_OPENMP_LIBOMPTARGET_SRC_MEMORYMANAGER_H

openmp/libomptarget/src/MemoryManager.cpp

-//===----------- MemoryManager.cpp - Target independent memory manager ----===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// Functionality for managing target memory.
-// It is very expensive to call alloc/free functions of target devices. The
-// MemoryManagerTy in this file is to reduce the number of invocations of those
-// functions by buffering allocated device memory. In this way, when a memory is
-// not used, it will not be freed on the device directly. The buffer is
-// organized in a number of buckets for efficient look up. A memory will go to
-// corresponding bucket based on its size. When a new memory request comes in,
-// it will first check whether there is free memory of same size. If yes,
-// returns it directly. Otherwise, allocate one on device.
-//
-// It also provides a way to opt out the memory manager. Memory
-// allocation/deallocation will only be managed if the requested size is less
-// than SizeThreshold, which can be configured via an environment variable
-// LIBOMPTARGET_MEMORY_MANAGER_THRESHOLD.
-//
-//===----------------------------------------------------------------------===//
-
-#include "MemoryManager.h"
-#include "device.h"
-#include "private.h"
-#include "rtl.h"
-
-namespace {
-constexpr const size_t BucketSize[] = {
-    0,       1U << 2, 1U << 3,  1U << 4,  1U << 5,  1U << 6, 1U << 7,
-    1U << 8, 1U << 9, 1U << 10, 1U << 11, 1U << 12, 1U << 13};
-
-constexpr const int NumBuckets = sizeof(BucketSize) / sizeof(BucketSize[0]);
-
-/// The threshold to manage memory using memory manager. If the request size is
-/// larger than \p SizeThreshold, the allocation will not be managed by the
-/// memory manager. This variable can be configured via an env \p
-/// LIBOMPTARGET_MEMORY_MANAGER_THRESHOLD. By default, the value is 8KB.
-size_t SizeThreshold = 1U << 13;
-
-/// Find the previous number that is power of 2 given a number that is not power
-/// of 2.
-size_t floorToPowerOfTwo(size_t Num) {
-  Num |= Num >> 1;
-  Num |= Num >> 2;
-  Num |= Num >> 4;
-  Num |= Num >> 8;
-  Num |= Num >> 16;
-#if INTPTR_MAX == INT64_MAX
-  Num |= Num >> 32;
-#elif INTPTR_MAX == INT32_MAX
-  // Do nothing with 32-bit
-#else
-#error Unsupported architecture
-#endif
-  Num += 1;
-  return Num >> 1;
-}
-
-/// Find a suitable bucket
-int findBucket(size_t Size) {
-  const size_t F = floorToPowerOfTwo(Size);
-
-  DP("findBucket: Size %zu is floored to %zu.\n", Size, F);
-
-  int L = 0, H = NumBuckets - 1;
-  while (H - L > 1) {
-    int M = (L + H) >> 1;
-    if (BucketSize[M] == F)
-      return M;
-    if (BucketSize[M] > F)
-      H = M - 1;
-    else
-      L = M;
-  }
-
-  assert(L >= 0 && L < NumBuckets && "L is out of range");
-
-  DP("findBucket: Size %zu goes to bucket %d\n", Size, L);
-
-  return L;
-}
-} // namespace
-
-MemoryManagerTy::MemoryManagerTy(DeviceTy &Dev, size_t Threshold)
-    : FreeLists(NumBuckets), FreeListLocks(NumBuckets), Device(Dev) {
-  if (Threshold)
-    SizeThreshold = Threshold;
-}
-
-MemoryManagerTy::~MemoryManagerTy() {
-  // TODO: There is a little issue that target plugin is destroyed before this
-  // object, therefore the memory free will not succeed.
-  // Deallocate all memory in map
-  for (auto Itr = PtrToNodeTable.begin(); Itr != PtrToNodeTable.end(); ++Itr) {
-    assert(Itr->second.Ptr && "nullptr in map table");
-    deleteOnDevice(Itr->second.Ptr);
-  }
-}
-
-void *MemoryManagerTy::allocateOnDevice(size_t Size, void *HstPtr) const {
-  return Device.RTL->data_alloc(Device.RTLDeviceID, Size, HstPtr);
-}
-
-int MemoryManagerTy::deleteOnDevice(void *Ptr) const {
-  return Device.RTL->data_delete(Device.RTLDeviceID, Ptr);
-}
-
-void *MemoryManagerTy::freeAndAllocate(size_t Size, void *HstPtr) {
-  std::vector<void *> RemoveList;
-
-  // Deallocate all memory in FreeList
-  for (int I = 0; I < NumBuckets; ++I) {
-    FreeListTy &List = FreeLists[I];
-    std::lock_guard<std::mutex> Lock(FreeListLocks[I]);
-    if (List.empty())
-      continue;
-    for (const NodeTy &N : List) {
-      deleteOnDevice(N.Ptr);
-      RemoveList.push_back(N.Ptr);
-    }
-    FreeLists[I].clear();
-  }
-
-  // Remove all nodes in the map table which have been released
-  if (!RemoveList.empty()) {
-    std::lock_guard<std::mutex> LG(MapTableLock);
-    for (void *P : RemoveList)
-      PtrToNodeTable.erase(P);
-  }
-
-  // Try allocate memory again
-  return allocateOnDevice(Size, HstPtr);
-}
-
-void *MemoryManagerTy::allocateOrFreeAndAllocateOnDevice(size_t Size,
-                                                         void *HstPtr) {
-  void *TgtPtr = allocateOnDevice(Size, HstPtr);
-  // We cannot get memory from the device. It might be due to OOM. Let's
-  // free all memory in FreeLists and try again.
-  if (TgtPtr == nullptr) {
-    DP("Failed to get memory on device. Free all memory in FreeLists and "
-       "try again.\n");
-    TgtPtr = freeAndAllocate(Size, HstPtr);
-  }
-
-#ifdef OMPTARGET_DEBUG
-  if (TgtPtr == nullptr)
-    DP("Still cannot get memory on device probably because the device is "
-       "OOM.\n");
-#endif
-
-  return TgtPtr;
-}
-
-void *MemoryManagerTy::allocate(size_t Size, void *HstPtr) {
-  // If the size is zero, we will not bother the target device. Just return
-  // nullptr directly.
-  if (Size == 0)
-    return nullptr;
-
-  DP("MemoryManagerTy::allocate: size %zu with host pointer " DPxMOD ".\n",
-     Size, DPxPTR(HstPtr));
-
-  // If the size is greater than the threshold, allocate it directly from
-  // device.
-  if (Size > SizeThreshold) {
-    DP("%zu is greater than the threshold %zu. Allocate it directly from "
-       "device\n",
-       Size, SizeThreshold);
-    void *TgtPtr = allocateOrFreeAndAllocateOnDevice(Size, HstPtr);
-
-    DP("Got target pointer " DPxMOD ". Return directly.\n", DPxPTR(TgtPtr));
-
-    return TgtPtr;
-  }
-
-  NodeTy *NodePtr = nullptr;
-
-  // Try to get a node from FreeList
-  {
-    const int B = findBucket(Size);
-    FreeListTy &List = FreeLists[B];
-
-    NodeTy TempNode(Size, nullptr);
-    std::lock_guard<std::mutex> LG(FreeListLocks[B]);
-    FreeListTy::const_iterator Itr = List.find(TempNode);
-
-    if (Itr != List.end()) {
-      NodePtr = &Itr->get();
-      List.erase(Itr);
-    }
-  }
-
-#ifdef OMPTARGET_DEBUG
-  if (NodePtr != nullptr)
-    DP("Find one node " DPxMOD " in the bucket.\n", DPxPTR(NodePtr));
-#endif
-
-  // We cannot find a valid node in FreeLists. Let's allocate on device and
-  // create a node for it.
-  if (NodePtr == nullptr) {
-    DP("Cannot find a node in the FreeLists. Allocate on device.\n");
-    // Allocate one on device
-    void *TgtPtr = allocateOrFreeAndAllocateOnDevice(Size, HstPtr);
-
-    if (TgtPtr == nullptr)
-      return nullptr;
-
-    // Create a new node and add it into the map table
-    {
-      std::lock_guard<std::mutex> Guard(MapTableLock);
-      auto Itr = PtrToNodeTable.emplace(TgtPtr, NodeTy(Size, TgtPtr));
-      NodePtr = &Itr.first->second;
-    }
-
-    DP("Node address " DPxMOD ", target pointer " DPxMOD ", size %zu\n",
-       DPxPTR(NodePtr), DPxPTR(TgtPtr), Size);
-  }
-
-  assert(NodePtr && "NodePtr should not be nullptr at this point");
-
-  return NodePtr->Ptr;
-}
-
-int MemoryManagerTy::free(void *TgtPtr) {
-  DP("MemoryManagerTy::free: target memory " DPxMOD ".\n", DPxPTR(TgtPtr));
-
-  NodeTy *P = nullptr;
-
-  // Look it up into the table
-  {
-    std::lock_guard<std::mutex> G(MapTableLock);
-    auto Itr = PtrToNodeTable.find(TgtPtr);
-
-    // We don't remove the node from the map table because the map does not
-    // change.
-    if (Itr != PtrToNodeTable.end())
-      P = &Itr->second;
-  }
-
-  // The memory is not managed by the manager
-  if (P == nullptr) {
-    DP("Cannot find its node. Delete it on device directly.\n");
-    return deleteOnDevice(TgtPtr);
-  }
-
-  // Insert the node to the free list
-  const int B = findBucket(P->Size);
-
-  DP("Found its node " DPxMOD ". Insert it to bucket %d.\n", DPxPTR(P), B);
-
-  {
-    std::lock_guard<std::mutex> G(FreeListLocks[B]);
-    FreeLists[B].insert(*P);
-  }
-
-  return OFFLOAD_SUCCESS;
-}

openmp/libomptarget/src/device.h

 
 #include "rtl.h"
 
 // Forward declarations.
 struct RTLInfoTy;
 struct __tgt_bin_desc;
 struct __tgt_target_table;
 struct __tgt_async_info;
-class MemoryManagerTy;
 
 using map_var_info_t = void *;
 
 // enum for OMP_TARGET_OFFLOAD; keep in sync with kmp.h definition
 enum kmp_target_offload_kind {
   tgt_disabled = 0,
   tgt_default = 1,
   tgt_mandatory = 2
struct DeviceTy {
   ShadowPtrListTy ShadowPtrMap;
 
   std::mutex DataMapMtx, PendingGlobalsMtx, ShadowMtx;
 
   // NOTE: Once libomp gains full target-task support, this state should be
   // moved into the target task in libomp.
   std::map<int32_t, uint64_t> LoopTripCnt;
 
-  /// Memory manager
-  std::unique_ptr<MemoryManagerTy> MemoryManager;
-
   DeviceTy(RTLInfoTy *RTL);
 
   // The existence of mutexes makes DeviceTy non-copyable. We need to
   // provide a copy constructor and an assignment operator explicitly.
   DeviceTy(const DeviceTy &D);
 
   DeviceTy &operator=(const DeviceTy &D);
 

openmp/libomptarget/src/device.cpp

 //===--------- device.cpp - Target independent OpenMP target RTL ----------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // Functionality for managing devices that are handled by RTL plugins.
 //
 //===----------------------------------------------------------------------===//
 
 #include "device.h"
-#include "MemoryManager.h"
 #include "private.h"
 #include "rtl.h"
 
 #include <cassert>
 #include <climits>
 #include <cstdio>
 #include <string>
 
 DeviceTy::DeviceTy(const DeviceTy &D)
     : DeviceID(D.DeviceID), RTL(D.RTL), RTLDeviceID(D.RTLDeviceID),
       IsInit(D.IsInit), InitFlag(), HasPendingGlobals(D.HasPendingGlobals),
       HostDataToTargetMap(D.HostDataToTargetMap),
       PendingCtorsDtors(D.PendingCtorsDtors), ShadowPtrMap(D.ShadowPtrMap),
       DataMapMtx(), PendingGlobalsMtx(), ShadowMtx(),
-      LoopTripCnt(D.LoopTripCnt), MemoryManager(nullptr) {}
+      LoopTripCnt(D.LoopTripCnt) {}
 
 DeviceTy &DeviceTy::operator=(const DeviceTy &D) {
   DeviceID = D.DeviceID;
   RTL = D.RTL;
   RTLDeviceID = D.RTLDeviceID;
   IsInit = D.IsInit;
   HasPendingGlobals = D.HasPendingGlobals;
   HostDataToTargetMap = D.HostDataToTargetMap;
   PendingCtorsDtors = D.PendingCtorsDtors;
   ShadowPtrMap = D.ShadowPtrMap;
   LoopTripCnt = D.LoopTripCnt;
 
   return *this;
 }
 
 DeviceTy::DeviceTy(RTLInfoTy *RTL)
     : DeviceID(-1), RTL(RTL), RTLDeviceID(-1), IsInit(false), InitFlag(),
       HasPendingGlobals(false), HostDataToTargetMap(), PendingCtorsDtors(),
-      ShadowPtrMap(), DataMapMtx(), PendingGlobalsMtx(), ShadowMtx(),
-      MemoryManager(nullptr) {}
+      ShadowPtrMap(), DataMapMtx(), PendingGlobalsMtx(), ShadowMtx() {}
 
 DeviceTy::~DeviceTy() {
   if (DeviceID == -1 || !(getInfoLevel() & OMP_INFOTYPE_DUMP_TABLE))
     return;
 
   ident_t loc = {0, 0, 0, 0, ";libomptarget;libomptarget;0;0;;"};
   dumpTargetPointerMappings(&loc, *this);
 }

 void DeviceTy::init() {
   // Make call to init_requires if it exists for this plugin.
   if (RTL->init_requires)
     RTL->init_requires(PM->RTLs.RequiresFlags);
   int32_t Ret = RTL->init_device(RTLDeviceID);
   if (Ret != OFFLOAD_SUCCESS)
     return;
 
-  // The memory manager will only be disabled when users provide a threshold via
-  // the environment variable \p LIBOMPTARGET_MEMORY_MANAGER_THRESHOLD and set
-  // it to 0.
-  if (const char *Env = std::getenv("LIBOMPTARGET_MEMORY_MANAGER_THRESHOLD")) {
-    size_t Threshold = std::stoul(Env);
-    if (Threshold)
-      MemoryManager = std::make_unique<MemoryManagerTy>(*this, Threshold);
-  } else
-    MemoryManager = std::make_unique<MemoryManagerTy>(*this);
-
   IsInit = true;
 }
 
 /// Thread-safe method to initialize the device only once.
 int32_t DeviceTy::initOnce() {
   std::call_once(InitFlag, &DeviceTy::init, this);
 
   // At this point, if IsInit is true, then either this thread or some other

 __tgt_target_table *DeviceTy::load_binary(void *Img) {
   RTL->Mtx.lock();
   __tgt_target_table *rc = RTL->load_binary(RTLDeviceID, Img);
   RTL->Mtx.unlock();
   return rc;
 }
 
 void *DeviceTy::allocData(int64_t Size, void *HstPtr) {
-  // If memory manager is enabled, we will allocate data via memory manager.
-  if (MemoryManager)
-    return MemoryManager->allocate(Size, HstPtr);
-
   return RTL->data_alloc(RTLDeviceID, Size, HstPtr);
 }
 
 int32_t DeviceTy::deleteData(void *TgtPtrBegin) {
-  // If memory manager is enabled, we will deallocate data via memory manager.
-  if (MemoryManager)
-    return MemoryManager->free(TgtPtrBegin);
-
   return RTL->data_delete(RTLDeviceID, TgtPtrBegin);
 }
 
 // Submit data to device
 int32_t DeviceTy::submitData(void *TgtPtrBegin, void *HstPtrBegin, int64_t Size,
                              __tgt_async_info *AsyncInfoPtr) {
   if (!AsyncInfoPtr || !RTL->data_submit_async || !RTL->synchronize)
     return RTL->data_submit(RTLDeviceID, TgtPtrBegin, HstPtrBegin, Size);