Imported Upstream version 16.07-rc1

[deb_dpdk.git] / doc / guides / prog_guide / mempool_lib.rst

diff --git a/doc/guides/prog_guide/mempool_lib.rst b/doc/guides/prog_guide/mempool_lib.rst
index 5fae79a..5946675 100644 (file)
--- a/doc/guides/prog_guide/mempool_lib.rst
+++ b/doc/guides/prog_guide/mempool_lib.rst
@@ -34,13 +34,12 @@ Mempool Library
 ===============
 
 A memory pool is an allocator of a fixed-sized object.
-In the DPDK, it is identified by name and uses a ring to store free objects.
+In the DPDK, it is identified by name and uses a mempool handler to store free objects.
+The default mempool handler is ring based.
 It provides some other optional services such as a per-core object cache and
 an alignment helper to ensure that objects are padded to spread them equally on all DRAM or DDR3 channels.
 
-This library is used by the
-:ref:`Mbuf Library <Mbuf_Library>` and the
-:ref:`Environment Abstraction Layer <Environment_Abstraction_Layer>` (for logging history).
+This library is used by the :ref:`Mbuf Library <Mbuf_Library>`.
 
 Cookies
 -------
@@ -116,7 +115,7 @@ While this may mean a number of buffers may sit idle on some core's cache,
 the speed at which a core can access its own cache for a specific memory pool without locks provides performance gains.
 
 The cache is composed of a small, per-core table of pointers and its length (used as a stack).
-This cache can be enabled or disabled at creation of the pool.
+This internal cache can be enabled or disabled at creation of the pool.
 
 The maximum size of the cache is static and is defined at compilation time (CONFIG_RTE_MEMPOOL_CACHE_MAX_SIZE).
 
@@ -128,6 +127,39 @@ The maximum size of the cache is static and is defined at compilation time (CONF
 
    A mempool in Memory with its Associated Ring
 
+Alternatively to the internal default per-lcore local cache, an application can create and manage external caches through the ``rte_mempool_cache_create()``, ``rte_mempool_cache_free()`` and ``rte_mempool_cache_flush()`` calls.
+These user-owned caches can be explicitly passed to ``rte_mempool_generic_put()`` and ``rte_mempool_generic_get()``.
+The ``rte_mempool_default_cache()`` call returns the default internal cache if any.
+In contrast to the default caches, user-owned caches can be used by non-EAL threads too.
+
+Mempool Handlers
+------------------------
+
+This allows external memory subsystems, such as external hardware memory
+management systems and software based memory allocators, to be used with DPDK.
+
+There are two aspects to a mempool handler.
+
+* Adding the code for your new mempool operations (ops). This is achieved by
+  adding a new mempool ops code, and using the ``REGISTER_MEMPOOL_OPS`` macro.
+
+* Using the new API to call ``rte_mempool_create_empty()`` and
+  ``rte_mempool_set_ops_byname()`` to create a new mempool and specifying which
+  ops to use.
+
+Several different mempool handlers may be used in the same application. A new
+mempool can be created by using the ``rte_mempool_create_empty()`` function,
+then using ``rte_mempool_set_ops_byname()`` to point the mempool to the
+relevant mempool handler callback (ops) structure.
+
+Legacy applications may continue to use the old ``rte_mempool_create()`` API
+call, which uses a ring based mempool handler by default. These applications
+will need to be modified to use a new mempool handler.
+
+For applications that use ``rte_pktmbuf_create()``, there is a config setting
+(``RTE_MBUF_DEFAULT_MEMPOOL_OPS``) that allows the application to make use of
+an alternative mempool handler.
+
 
 Use Cases
 ---------