Remove the additional host register calls initially intended for perf…

…ormance improvement on Grace Hopper

cpp/src/io/utilities/datasource.cpp

@@ -134,27 +134,6 @@ class file_source : public datasource {
   static constexpr size_t _gds_read_preferred_threshold = 128 << 10;  // 128KB
 };
 
-/**
- * @brief Memoized pageableMemoryAccessUsesHostPageTables device property.
- */
-[[nodiscard]] bool pageableMemoryAccessUsesHostPageTables()
-{
-  static std::unordered_map<int, bool> result_cache{};
-
-  int deviceId{};
-  CUDF_CUDA_TRY(cudaGetDevice(&deviceId));
-
-  if (result_cache.find(deviceId) == result_cache.end()) {
-    cudaDeviceProp props{};
-    CUDF_CUDA_TRY(cudaGetDeviceProperties(&props, deviceId));
-    result_cache[deviceId] = (props.pageableMemoryAccessUsesHostPageTables == 1);
-    CUDF_LOG_INFO(
-      "Device {} pageableMemoryAccessUsesHostPageTables: {}", deviceId, result_cache[deviceId]);
-  }
-
-  return result_cache[deviceId];
-}
-
 /**
  * @brief Implementation class for reading from a file using memory mapped access.
  *
@@ -172,19 +151,12 @@ class memory_mapped_source : public file_source {
     if (_file.size() != 0) {
       // Memory mapping is not exclusive, so we can include the whole region we expect to read
       map(_file.desc(), offset, max_size_estimate);
-      // Buffer registration is exclusive (can't overlap with other registered buffers) so we
-      // register the lower estimate; this avoids issues when reading adjacent ranges from the same
-      // file from multiple threads
-      register_mmap_buffer(offset, min_size_estimate);
     }
   }
 
   ~memory_mapped_source() override
   {
-    if (_map_addr != nullptr) {
-      unmap();
-      unregister_mmap_buffer();
-    }
+    if (_map_addr != nullptr) { unmap(); }
   }
 
   std::unique_ptr<buffer> host_read(size_t offset, size_t size) override
@@ -227,46 +199,6 @@ class memory_mapped_source : public file_source {
   }
 
  private:
-  /**
-   * @brief Page-locks (registers) the memory range of the mapped file.
-   *
-   * Fixes nvbugs/4215160
-   */
-  void register_mmap_buffer(size_t offset, size_t size)
-  {
-    if (_map_addr == nullptr or not pageableMemoryAccessUsesHostPageTables()) { return; }
-
-    // Registered region must be within the mapped region
-    _reg_offset = std::max(offset, _map_offset);
-    _reg_size   = std::min(size != 0 ? size : _map_size, (_map_offset + _map_size) - _reg_offset);
-
-    _reg_addr         = static_cast<std::byte*>(_map_addr) - _map_offset + _reg_offset;
-    auto const result = cudaHostRegister(_reg_addr, _reg_size, cudaHostRegisterReadOnly);
-    if (result != cudaSuccess) {
-      _reg_addr = nullptr;
-      CUDF_LOG_WARN("cudaHostRegister failed with {} ({})",
-                    static_cast<int>(result),
-                    cudaGetErrorString(result));
-    }
-  }
-
-  /**
-   * @brief Unregisters the memory range of the mapped file.
-   */
-  void unregister_mmap_buffer()
-  {
-    if (_reg_addr == nullptr) { return; }
-
-    auto const result = cudaHostUnregister(_reg_addr);
-    if (result == cudaSuccess) {
-      _reg_addr = nullptr;
-    } else {
-      CUDF_LOG_WARN("cudaHostUnregister failed with {} ({})",
-                    static_cast<int>(result),
-                    cudaGetErrorString(result));
-    }
-  }
-
   void map(int fd, size_t offset, size_t size)
   {
     CUDF_EXPECTS(offset < _file.size(), "Offset is past end of file", std::overflow_error);