ARROW-830: [Python] Expose jemalloc memory pool and other memory pool functions in public pyarrow API

python/README.md

@@ -89,7 +89,7 @@ export PYARROW_CMAKE_OPTIONS=-DPYARROW_BUILD_PARQUET=on
 
 ```bash
 pip install -r doc/requirements.txt
-python setup.py build_sphinx
+python setup.py build_sphinx -s doc/source
 ```
 
 [1]: https://github.com/apache/parquet-cpp

python/doc/source/api.rst

@@ -151,3 +151,15 @@ Interprocess Communication and Messaging
    FileWriter
    StreamReader
    StreamWriter
+
+Memory Pools
+------------
+
+.. autosummary::
+   :toctree: generated/
+
+   MemoryPool
+   default_memory_pool
+   jemalloc_memory_pool
+   total_allocated_bytes
+   set_memory_pool

python/doc/source/jemalloc.rst

@@ -35,18 +35,14 @@ operations.
 .. code:: python
 
     import pyarrow as pa
-    import pyarrow.jemalloc
-    import pyarrow.memory
 
-    jemalloc_pool = pyarrow.jemalloc.default_pool()
+    jemalloc_pool = pyarrow.jemalloc_memory_pool()
 
     # Explicitly use jemalloc for allocating memory for an Arrow Table object
     array = pa.Array.from_pylist([1, 2, 3], memory_pool=jemalloc_pool)
 
     # Set the global pool
-    pyarrow.memory.set_default_pool(jemalloc_pool)
+    pyarrow.set_memory_pool(jemalloc_pool)
     # This operation has no explicit MemoryPool specified and will thus will
     # also use jemalloc for its allocations.
     array = pa.Array.from_pylist([1, 2, 3])
-
-

python/pyarrow/__init__.py

@@ -62,7 +62,8 @@
                          memory_map, create_memory_map,
                          get_record_batch_size, get_tensor_size)
 
-from pyarrow._memory import MemoryPool, total_allocated_bytes
+from pyarrow._memory import (MemoryPool, total_allocated_bytes,
+                             set_memory_pool, default_memory_pool)
 from pyarrow._table import Column, RecordBatch, Table, concat_tables
 from pyarrow._error import (ArrowException,
                             ArrowKeyError,
@@ -72,6 +73,16 @@
                             ArrowNotImplementedError,
                             ArrowTypeError)
 
+
+def jemalloc_memory_pool():
+    """
+    Returns a jemalloc-based memory allocator, which can be passed to
+    pyarrow.set_memory_pool
+    """
+    from pyarrow._jemalloc import default_pool
+    return default_pool()
+
+
 from pyarrow.filesystem import Filesystem, HdfsClient, LocalFilesystem
 
 from pyarrow.ipc import FileReader, FileWriter, StreamReader, StreamWriter

python/pyarrow/_memory.pyx

@@ -22,31 +22,37 @@
 from pyarrow.includes.libarrow cimport CMemoryPool, CLoggingMemoryPool
 from pyarrow.includes.pyarrow cimport set_default_memory_pool, get_memory_pool
 
+
 cdef class MemoryPool:
     cdef init(self, CMemoryPool* pool):
         self.pool = pool
 
     def bytes_allocated(self):
         return self.pool.bytes_allocated()
 
+
 cdef CMemoryPool* maybe_unbox_memory_pool(MemoryPool memory_pool):
     if memory_pool is None:
         return get_memory_pool()
     else:
         return memory_pool.pool
 
+
 cdef class LoggingMemoryPool(MemoryPool):
     pass
 
-def default_pool():
-    cdef: 
+
+def default_memory_pool():
+    cdef:
         MemoryPool pool = MemoryPool()
     pool.init(get_memory_pool())
     return pool
 
-def set_default_pool(MemoryPool pool):
+
+def set_memory_pool(MemoryPool pool):
     set_default_memory_pool(pool.pool)
 
+
 def total_allocated_bytes():
     cdef CMemoryPool* pool = get_memory_pool()
     return pool.bytes_allocated()

python/pyarrow/tests/test_jemalloc.py

@@ -18,46 +18,50 @@
 import gc
 import pytest
 
+import pyarrow as pa
+
+
 try:
-    import pyarrow.jemalloc
+    pa.jemalloc_memory_pool()
     HAVE_JEMALLOC = True
 except ImportError:
     HAVE_JEMALLOC = False
 
+
 jemalloc = pytest.mark.skipif(not HAVE_JEMALLOC,
                               reason='jemalloc support not built')
 
 
 @jemalloc
 def test_different_memory_pool():
     gc.collect()
-    bytes_before_default = pyarrow.total_allocated_bytes()
-    bytes_before_jemalloc = pyarrow.jemalloc.default_pool().bytes_allocated()
+    bytes_before_default = pa.total_allocated_bytes()
+    bytes_before_jemalloc = pa.jemalloc_memory_pool().bytes_allocated()
 
     # it works
-    array = pyarrow.from_pylist([1, None, 3, None],  # noqa
-                                memory_pool=pyarrow.jemalloc.default_pool())
+    array = pa.from_pylist([1, None, 3, None],  # noqa
+                                memory_pool=pa.jemalloc_memory_pool())
     gc.collect()
-    assert pyarrow.total_allocated_bytes() == bytes_before_default
-    assert (pyarrow.jemalloc.default_pool().bytes_allocated() >
+    assert pa.total_allocated_bytes() == bytes_before_default
+    assert (pa.jemalloc_memory_pool().bytes_allocated() >
             bytes_before_jemalloc)
 
 
 @jemalloc
 def test_default_memory_pool():
     gc.collect()
-    bytes_before_default = pyarrow.total_allocated_bytes()
-    bytes_before_jemalloc = pyarrow.jemalloc.default_pool().bytes_allocated()
+    bytes_before_default = pa.total_allocated_bytes()
+    bytes_before_jemalloc = pa.jemalloc_memory_pool().bytes_allocated()
 
-    old_memory_pool = pyarrow.memory.default_pool()
-    pyarrow.memory.set_default_pool(pyarrow.jemalloc.default_pool())
+    old_memory_pool = pa.default_memory_pool()
+    pa.set_memory_pool(pa.jemalloc_memory_pool())
 
-    array = pyarrow.from_pylist([1, None, 3, None])  # noqa
+    array = pa.from_pylist([1, None, 3, None])  # noqa
 
-    pyarrow.memory.set_default_pool(old_memory_pool)
+    pa.set_memory_pool(old_memory_pool)
     gc.collect()
 
-    assert pyarrow.total_allocated_bytes() == bytes_before_default
+    assert pa.total_allocated_bytes() == bytes_before_default
 
-    assert (pyarrow.jemalloc.default_pool().bytes_allocated() >
+    assert (pa.jemalloc_memory_pool().bytes_allocated() >
             bytes_before_jemalloc)