From patchwork Tue May 12 08:03:02 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Phil Yang X-Patchwork-Id: 70097 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 B4EC5A04A2; Tue, 12 May 2020 10:03:58 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 8E8651C00D; Tue, 12 May 2020 10:03:58 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by dpdk.org (Postfix) with ESMTP id 38C951BF59 for ; Tue, 12 May 2020 10:03:57 +0200 (CEST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ABE321FB; Tue, 12 May 2020 01:03:56 -0700 (PDT) Received: from phil-VirtualBox.shanghai.arm.com (phil-VirtualBox.shanghai.arm.com [10.169.109.147]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 47E143F305; Tue, 12 May 2020 01:03:43 -0700 (PDT) From: Phil Yang To: thomas@monjalon.net, dev@dpdk.org Cc: bruce.richardson@intel.com, ferruh.yigit@intel.com, hemant.agrawal@nxp.com, honnappa.nagarahalli@arm.com, jerinj@marvell.com, ktraynor@redhat.com, konstantin.ananyev@intel.com, maxime.coquelin@redhat.com, olivier.matz@6wind.com, stephen@networkplumber.org, mb@smartsharesystems.com, mattias.ronnblom@ericsson.com, harry.van.haaren@intel.com, erik.g.carrillo@intel.com, phil.yang@arm.com, nd@arm.com Date: Tue, 12 May 2020 16:03:02 +0800 Message-Id: <1589270586-4480-1-git-send-email-phil.yang@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1584407863-774-1-git-send-email-phil.yang@arm.com> References: <1584407863-774-1-git-send-email-phil.yang@arm.com> Subject: [dpdk-dev] [PATCH v4 0/4] generic rte atomic APIs deprecate proposal 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" DPDK provides generic rte_atomic APIs to do several atomic operations. These APIs are using the deprecated __sync built-ins and enforce full memory barriers on aarch64. However, full barriers are not necessary in many use cases. In order to address such use cases, C language offers C11 atomic APIs. The C11 atomic APIs provide finer memory barrier control by making use of the memory ordering parameter provided by the user. Various patches submitted in the past [2] and the patches in this series indicate significant performance gains on multiple aarch64 CPUs and no performance loss on x86. But the existing rte_atomic API implementations cannot be changed as the APIs do not take the memory ordering parameter. The only choice available is replacing the usage of the rte_atomic APIs with C11 atomic APIs. In order to make this change, the following steps are proposed: [1] deprecate rte_atomic APIs so that future patches do not use rte_atomic APIs (a script is added to flag the usages). [2] refactor the code that uses rte_atomic APIs to use c11 atomic APIs. This patchset contains: 1) changes to programmer guide describing writing efficient code for aarch64. 2) the checkpatch script changes to flag rte_atomicNN_xxx API usage in patches. 3) wraps up compiler __atomic built-ins with explicit memory ordering parameter. v4: 1. add reader-writer concurrency case describing. 2. claim maintainership of c11 atomics code for each platforms. 3. flag rte_atomicNN_xxx in new patches for modules that have been converted to c11 style. 4. flag __sync_xxx built-ins in new patches. 5. wraps up compiler atomic built-ins 6. move the changes of libraries which make use of c11 atomic APIs out of this patchset. v3: add libatomic dependency for 32-bit clang v2: 1. fix Clang '-Wincompatible-pointer-types' WARNING. 2. fix typos. Phil Yang (4): doc: add generic atomic deprecation section maintainers: claim maintainers of c11 atomics code devtools: prevent use of rte atomic APIs in future patches eal/atomic: add wrapper for c11 atomics MAINTAINERS | 4 + devtools/checkpatches.sh | 23 ++++ doc/guides/prog_guide/writing_efficient_code.rst | 139 ++++++++++++++++++++++- lib/librte_eal/include/generic/rte_atomic_c11.h | 139 +++++++++++++++++++++++ lib/librte_eal/include/meson.build | 1 + 5 files changed, 305 insertions(+), 1 deletion(-) create mode 100644 lib/librte_eal/include/generic/rte_atomic_c11.h