Make device_buffer streams explicit and enforce move construction

cpp/benchmarks/iterator/iterator_benchmark.cu

@@ -50,7 +50,7 @@ inline auto reduce_by_cub(OutputIterator result, InputIterator d_in, int num_ite
     nullptr, temp_storage_bytes, d_in, result, num_items, cudf::DeviceSum{}, init);
 
   // Allocate temporary storage
-  rmm::device_buffer d_temp_storage(temp_storage_bytes);
+  rmm::device_buffer d_temp_storage(temp_storage_bytes, rmm::cuda_stream_default);
 
   // Run reduction
   cub::DeviceReduce::Reduce(

cpp/benchmarks/type_dispatcher/type_dispatcher_benchmark.cu

@@ -16,6 +16,7 @@
 
 #include "../fixture/benchmark_fixture.hpp"
 #include "../synchronization/synchronization.hpp"
+#include "rmm/device_buffer.hpp"
 
 #include <cudf_test/column_wrapper.hpp>
 
@@ -186,10 +187,12 @@ void type_dispatcher_benchmark(::benchmark::State& state)
   cudf::mutable_table_view source_table{source_columns};
 
   // For no dispatching
-  std::vector<rmm::device_buffer> h_vec(n_cols,
-                                        rmm::device_buffer(source_size * sizeof(TypeParam)));
+  std::vector<rmm::device_buffer> h_vec(n_cols);
   std::vector<TypeParam*> h_vec_p(n_cols);
-  for (int c = 0; c < n_cols; c++) { h_vec_p[c] = static_cast<TypeParam*>(h_vec[c].data()); }
+  std::transform(h_vec.begin(), h_vec.end(), h_vec_p.begin(), [source_size](auto& col) {
+    col.resize(source_size * sizeof(TypeParam), rmm::cuda_stream_default);
+    return static_cast<TypeParam*>(col.data());
+  });
   rmm::device_uvector<TypeParam*> d_vec(n_cols, rmm::cuda_stream_default);
 
   if (dispatching_type == NO_DISPATCHING) {

cpp/docs/DEVELOPER_GUIDE.md

@@ -414,21 +414,25 @@ Allocates a specified number of bytes of untyped, uninitialized device memory us
 `device_memory_resource`. If no resource is explicitly provided, uses 
 `rmm::mr::get_current_device_resource()`. 
 
-`rmm::device_buffer` is copyable and movable. A copy performs a deep copy of the `device_buffer`'s 
-device memory, whereas a move moves ownership of the device memory from one `device_buffer` to 
-another.
+`rmm::device_buffer` is movable and copyable on a stream. A copy performs a deep copy of the 
+`device_buffer`'s device memory on the specified stream, whereas a move moves ownership of the 
+device memory from one `device_buffer` to another.
 
 ```c++
 // Allocates at least 100 bytes of uninitialized device memory 
 // using the specified resource and stream
 rmm::device_buffer buff(100, stream, mr); 
 void * raw_data = buff.data(); // Raw pointer to underlying device memory
 
-rmm::device_buffer copy(buff); // Deep copies `buff` into `copy`
-rmm::device_buffer moved_to(std::move(buff)); // Moves contents of `buff` into `moved_to`
+// Deep copies `buff` into `copy` on `stream`
+rmm::device_buffer copy(buff, stream); 
+
+// Moves contents of `buff` into `moved_to`
+rmm::device_buffer moved_to(std::move(buff)); 
 
 custom_memory_resource *mr...;
-rmm::device_buffer custom_buff(100, mr); // Allocates 100 bytes from the custom_memory_resource
+// Allocates 100 bytes from the custom_memory_resource
+rmm::device_buffer custom_buff(100, mr, stream); 
 ```
 
 #### `rmm::device_scalar<T>`

cpp/include/cudf/column/column.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2020, NVIDIA CORPORATION.
+ * Copyright (c) 2019-2021, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -49,13 +49,6 @@ class column {
   column& operator=(column const& other) = delete;
   column& operator=(column&& other) = delete;
 
-  /**
-   * @brief Construct a new column by deep copying the contents of `other`.
-   *
-   * @param other The column to copy
-   */
-  column(column const& other);
-
   /**
    * @brief Construct a new column object by deep copying the contents of
    *`other`.
@@ -68,7 +61,7 @@ class column {
    * @param mr Device memory resource to use for all device memory allocations
    */
   column(column const& other,
-         rmm::cuda_stream_view stream,
+         rmm::cuda_stream_view stream        = rmm::cuda_stream_view{},
          rmm::mr::device_memory_resource* mr = rmm::mr::get_current_device_resource());
 
   /**
@@ -165,18 +158,21 @@ class column {
   /**
    * @brief Sets the column's null value indicator bitmask to `new_null_mask`.
    *
-   * @throws cudf::logic_error if new_null_count is larger than 0 and the size
-   * of `new_null_mask` does not match the size of this column.
-   *
-   * @param new_null_mask New null value indicator bitmask (lvalue overload &
-   * copied) to set the column's null value indicator mask. May be empty if
-   * `new_null_count` is 0 or `UNKOWN_NULL_COUNT`.
-   * @param new_null_count Optional, the count of null elements. If unknown,
-   * specify `UNKNOWN_NULL_COUNT` to indicate that the null count should be
-   * computed on the first invocation of `null_count()`.
+   * @throws cudf::logic_error if new_null_count is larger than 0 and the size of `new_null_mask`
+   * does not match the size of this column.
+   *
+   * @param new_null_mask New null value indicator bitmask (lvalue overload & copied) to set the
+   * column's null value indicator mask. May be empty if `new_null_count` is 0 or
+   * `UNKOWN_NULL_COUNT`.
+   * @param new_null_count Optional, the count of null elements. If unknown, specify
+   * `UNKNOWN_NULL_COUNT` to indicate that the null count should be computed on the first invocation
+   * of `null_count()`.
+   * @param stream The stream on which to perform the allocation and copy. Uses the default CUDA
+   * stream if none is specified.
    */
   void set_null_mask(rmm::device_buffer const& new_null_mask,
-                     size_type new_null_count = UNKNOWN_NULL_COUNT);
+                     size_type new_null_count     = UNKNOWN_NULL_COUNT,
+                     rmm::cuda_stream_view stream = rmm::cuda_stream_view{});
 
   /**
    * @brief Updates the count of null elements.

cpp/include/cudf/lists/detail/scatter.cuh

@@ -337,7 +337,7 @@ struct list_child_constructor {
     auto const num_child_rows{
       cudf::detail::get_value<size_type>(list_offsets, list_offsets.size() - 1, stream)};
 
-    auto const child_null_mask =
+    auto child_null_mask =
       source_lists_column_view.child().nullable() || target_lists_column_view.child().nullable()
         ? construct_child_nullmask(
             list_vector, list_offsets, source_lists, target_lists, num_child_rows, stream, mr)
@@ -354,7 +354,7 @@ struct list_child_constructor {
 
     auto child_column = cudf::make_fixed_width_column(source_lists_column_view.child().type(),
                                                       num_child_rows,
-                                                      child_null_mask.first,
+                                                      std::move(child_null_mask.first),
                                                       child_null_mask.second,
                                                       stream,
                                                       mr);
@@ -652,7 +652,7 @@ struct list_child_constructor {
                                      std::make_unique<column>(structs_list_offsets, stream, mr),
                                      std::make_unique<column>(structs_member, stream, mr),
                                      structs_list_null_count,
-                                     rmm::device_buffer(structs_list_nullmask),
+                                     rmm::device_buffer(structs_list_nullmask, stream),
                                      stream,
                                      mr);
     };