[GitHub] [arrow] davisusanibar commented on a change in pull request #12603: ARROW-15573: [Java][Doc] Apache Arrow memory management

[GitBox <gi...@apache.org>]

davisusanibar commented on a change in pull request #12603:
URL: https://github.com/apache/arrow/pull/12603#discussion_r826442304



##########
File path: docs/source/java/memory.rst
##########
@@ -0,0 +1,82 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements.  See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership.  The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License.  You may obtain a copy of the License at
+
+..   http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied.  See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+=================
+Memory Management
+=================
+
+The memory management package contains all the memory allocation related items that Arrow uses to manage memory.
+This section will introduce you to the major concepts in Java’s memory management:
+
+* Allocator
+* Arrowbuf
+
+.. contents::
+
+Getting Started
+===============
+
+Java memory implementation is independently from C++ (not a wrapper around).
+Java memory was implemented considering these specifications: Arrow Columnar Format and Java Off Heap references.
+
+.. note::
+
+    Java Memory Data = Data (Columnar mode reference) + Metadata (Flatbuffers serialization reference).
+
+These are the java memory modules:
+
+* Memory Core: Core off-heap memory management libraries for Arrow ValueVectors.
+* Memory Netty: Netty allocator and utils for allocating memory in Arrow.
+* Memory Unsafe: Allocator and utils for allocating memory in Arrow based on sun.misc.Unsafe.
+
+Allocators
+==========
+
+Memory core module define the next allocators:
+
+* Buffer Allocator: The public interface application users should be leveraging.
+* Root Allocator: A root allocator for using direct memory. Typically only one created for a JVM.
+
+Arrow provides a tree-based model for memory allocation. The RootAllocator is created first,
+then all allocators are created as children of that allocator. The RootAllocator is responsible
+for being the master bookkeeper for memory allocations.
+
+Please consider this note on your development:
+
+* Use BufferAllocator instead of RootAllocator in your allocator creation.
+* Create your allocator inside of a try-with-resources statement.
+
+.. code-block:: Java
+
+    try (BufferAllocator allocator = new RootAllocator(Long.MAX_VALUE) ) { ; }
+
+ArrowBuf
+========
+
+The facade for interacting directly with a chunk of memory.
+
+Two important instance variables of an ArrowBuf:
+
+* Address: Starting virtual address in the underlying memory chunk that this ArrowBuf has access to.
+* Length: Length (in bytes) in the underlying memory chunk that this ArrowBuf has access to.

Review comment:
       Deleted

##########
File path: docs/source/java/memory.rst
##########
@@ -0,0 +1,82 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements.  See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership.  The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License.  You may obtain a copy of the License at
+
+..   http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied.  See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+=================
+Memory Management
+=================
+
+The memory management package contains all the memory allocation related items that Arrow uses to manage memory.
+This section will introduce you to the major concepts in Java’s memory management:
+
+* Allocator
+* Arrowbuf
+
+.. contents::
+
+Getting Started
+===============
+
+Java memory implementation is independently from C++ (not a wrapper around).
+Java memory was implemented considering these specifications: Arrow Columnar Format and Java Off Heap references.
+
+.. note::
+
+    Java Memory Data = Data (Columnar mode reference) + Metadata (Flatbuffers serialization reference).
+
+These are the java memory modules:
+
+* Memory Core: Core off-heap memory management libraries for Arrow ValueVectors.
+* Memory Netty: Netty allocator and utils for allocating memory in Arrow.
+* Memory Unsafe: Allocator and utils for allocating memory in Arrow based on sun.misc.Unsafe.
+
+Allocators
+==========
+
+Memory core module define the next allocators:
+
+* Buffer Allocator: The public interface application users should be leveraging.
+* Root Allocator: A root allocator for using direct memory. Typically only one created for a JVM.
+
+Arrow provides a tree-based model for memory allocation. The RootAllocator is created first,
+then all allocators are created as children of that allocator. The RootAllocator is responsible
+for being the master bookkeeper for memory allocations.
+
+Please consider this note on your development:
+
+* Use BufferAllocator instead of RootAllocator in your allocator creation.
+* Create your allocator inside of a try-with-resources statement.
+
+.. code-block:: Java
+
+    try (BufferAllocator allocator = new RootAllocator(Long.MAX_VALUE) ) { ; }
+
+ArrowBuf
+========
+
+The facade for interacting directly with a chunk of memory.

Review comment:
       Added

##########
File path: docs/source/java/memory.rst
##########
@@ -0,0 +1,82 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements.  See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership.  The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License.  You may obtain a copy of the License at
+
+..   http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied.  See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+=================
+Memory Management
+=================
+
+The memory management package contains all the memory allocation related items that Arrow uses to manage memory.
+This section will introduce you to the major concepts in Java’s memory management:
+
+* Allocator
+* Arrowbuf
+
+.. contents::
+
+Getting Started
+===============
+
+Java memory implementation is independently from C++ (not a wrapper around).
+Java memory was implemented considering these specifications: Arrow Columnar Format and Java Off Heap references.
+
+.. note::
+
+    Java Memory Data = Data (Columnar mode reference) + Metadata (Flatbuffers serialization reference).
+
+These are the java memory modules:
+
+* Memory Core: Core off-heap memory management libraries for Arrow ValueVectors.
+* Memory Netty: Netty allocator and utils for allocating memory in Arrow.
+* Memory Unsafe: Allocator and utils for allocating memory in Arrow based on sun.misc.Unsafe.
+
+Allocators
+==========
+
+Memory core module define the next allocators:
+
+* Buffer Allocator: The public interface application users should be leveraging.
+* Root Allocator: A root allocator for using direct memory. Typically only one created for a JVM.
+
+Arrow provides a tree-based model for memory allocation. The RootAllocator is created first,
+then all allocators are created as children of that allocator. The RootAllocator is responsible
+for being the master bookkeeper for memory allocations.
+
+Please consider this note on your development:
+
+* Use BufferAllocator instead of RootAllocator in your allocator creation.

Review comment:
       Updated

##########
File path: docs/source/java/memory.rst
##########
@@ -0,0 +1,82 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements.  See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership.  The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License.  You may obtain a copy of the License at
+
+..   http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied.  See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+=================
+Memory Management
+=================
+
+The memory management package contains all the memory allocation related items that Arrow uses to manage memory.
+This section will introduce you to the major concepts in Java’s memory management:
+
+* Allocator
+* Arrowbuf
+
+.. contents::
+
+Getting Started
+===============
+
+Java memory implementation is independently from C++ (not a wrapper around).
+Java memory was implemented considering these specifications: Arrow Columnar Format and Java Off Heap references.

Review comment:
       Added




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