From patchwork Mon Aug 24 16:13:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eads, Gage" X-Patchwork-Id: 75888 X-Patchwork-Delegate: thomas@monjalon.net Return-Path: X-Original-To: patchwork@inbox.dpdk.org Delivered-To: patchwork@inbox.dpdk.org Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id D49CDA04B1; Mon, 24 Aug 2020 18:16:17 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id D0549F12; Mon, 24 Aug 2020 18:16:16 +0200 (CEST) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by dpdk.org (Postfix) with ESMTP id ED821DE3 for ; Mon, 24 Aug 2020 18:16:14 +0200 (CEST) IronPort-SDR: KwkEmlweCGkSITkx0zXJDnYA9vD+/MUD7poVMe/6ycRQMLnlP+Kov+niMYUqGJkekO13giDelk y4n4z+RmfJ1g== X-IronPort-AV: E=McAfee;i="6000,8403,9723"; a="240754187" X-IronPort-AV: E=Sophos;i="5.76,349,1592895600"; d="scan'208";a="240754187" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Aug 2020 09:16:11 -0700 IronPort-SDR: 7Huza0OvTbMA/K9f9s7MKqb2FXjARaGbmqBgq+1Dv0iMFc0NEYhsh9GeEelDF3wkrDtPdWTN00 t9vINdmJhb4Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,349,1592895600"; d="scan'208";a="499527384" Received: from txasoft-yocto.an.intel.com ([10.123.72.192]) by fmsmga005.fm.intel.com with ESMTP; 24 Aug 2020 09:16:11 -0700 From: Gage Eads To: dev@dpdk.org Cc: olivier.matz@6wind.com, arybchenko@solarflare.com, john.mcnamara@intel.com, marko.kovacevic@intel.com Date: Mon, 24 Aug 2020 11:13:06 -0500 Message-Id: <20200824161306.12660-1-gage.eads@intel.com> X-Mailer: git-send-email 2.13.6 In-Reply-To: <20200811211015.29704-1-gage.eads@intel.com> References: <20200811211015.29704-1-gage.eads@intel.com> Subject: [dpdk-dev] [PATCH] doc: add stack mempool guide X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" This guide describes the two stack modes, their tradeoffs, and (via a reference to the mempool guide) how to enable them. Signed-off-by: Gage Eads --- v2: Added commit description doc/guides/mempool/index.rst | 1 + doc/guides/mempool/stack.rst | 38 +++++++++++++++++++++++++++++++++++ doc/guides/prog_guide/mempool_lib.rst | 2 ++ doc/guides/prog_guide/stack_lib.rst | 4 ++++ 4 files changed, 45 insertions(+) create mode 100644 doc/guides/mempool/stack.rst diff --git a/doc/guides/mempool/index.rst b/doc/guides/mempool/index.rst index bbd02fd81..a0e55467e 100644 --- a/doc/guides/mempool/index.rst +++ b/doc/guides/mempool/index.rst @@ -14,3 +14,4 @@ application through the mempool API. octeontx octeontx2 ring + stack diff --git a/doc/guides/mempool/stack.rst b/doc/guides/mempool/stack.rst new file mode 100644 index 000000000..3baa774f3 --- /dev/null +++ b/doc/guides/mempool/stack.rst @@ -0,0 +1,38 @@ +.. SPDX-License-Identifier: BSD-3-Clause + Copyright(c) 2020 Intel Corporation. + +Stack Mempool Driver +=================== + +**rte_mempool_stack** is a pure software mempool driver based on the +``rte_stack`` DPDK library. A stack-based mempool is often better suited to +packet-processing workloads than a ring-based mempool, since its LIFO behavior +results in better temporal locality and a minimal memory footprint even if the +mempool is over-provisioned. + +The following modes of operation are available for the stack mempool driver and +can be selected as described in :ref:`Mempool_Handlers`: + +- ``stack`` + + The underlying **rte_stack** operates in standard (lock-based) mode. + For more information please refer to :ref:`Stack_Library_Std_Stack`. + +- ``lf_stack`` + + The underlying **rte_stack** operates in lock-free mode. For more + information please refer to :ref:`Stack_Library_LF_Stack`. + +The standard stack outperforms the lock-free stack on average, however the +standard stack is non-preemptive: if a mempool user is preempted while holding +the stack lock, that thread will block all other mempool accesses until it +returns and releases the lock. As a result, an application using the standard +stack whose threads can be preempted can suffer from brief, infrequent +performance hiccups. + +The lock-free stack, by design, is not susceptible to this problem; one thread can +be preempted at any point during a push or pop operation and will not impede +the progress of any other thread. + +For a more detailed description of the stack implementations, please refer to +:doc:`../prog_guide/stack_lib`. diff --git a/doc/guides/prog_guide/mempool_lib.rst b/doc/guides/prog_guide/mempool_lib.rst index e3e1f940b..6f3c0067f 100644 --- a/doc/guides/prog_guide/mempool_lib.rst +++ b/doc/guides/prog_guide/mempool_lib.rst @@ -105,6 +105,8 @@ These user-owned caches can be explicitly passed to ``rte_mempool_generic_put()` 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 unregistered non-EAL threads too. +.. _Mempool_Handlers: + Mempool Handlers ------------------------ diff --git a/doc/guides/prog_guide/stack_lib.rst b/doc/guides/prog_guide/stack_lib.rst index 8fe8804e3..3097cab0c 100644 --- a/doc/guides/prog_guide/stack_lib.rst +++ b/doc/guides/prog_guide/stack_lib.rst @@ -28,6 +28,8 @@ Implementation The library supports two types of stacks: standard (lock-based) and lock-free. Both types use the same set of interfaces, but their implementations differ. +.. _Stack_Library_Std_Stack: + Lock-based Stack ---------------- @@ -35,6 +37,8 @@ The lock-based stack consists of a contiguous array of pointers, a current index, and a spinlock. Accesses to the stack are made multi-thread safe by the spinlock. +.. _Stack_Library_LF_Stack: + Lock-free Stack ------------------