+ David Christensen The PPC c11 atomics maintainer.
My apologies, I forgot to cc you on this email. Thanks, Phil Yang > -----Original Message----- > From: Phil Yang <phil.y...@arm.com> > Sent: Tuesday, May 12, 2020 4:03 PM > To: tho...@monjalon.net; dev@dpdk.org > Cc: bruce.richard...@intel.com; ferruh.yi...@intel.com; > hemant.agra...@nxp.com; Honnappa Nagarahalli > <honnappa.nagaraha...@arm.com>; jer...@marvell.com; > ktray...@redhat.com; konstantin.anan...@intel.com; > maxime.coque...@redhat.com; olivier.m...@6wind.com; > step...@networkplumber.org; m...@smartsharesystems.com; > mattias.ronnb...@ericsson.com; harry.van.haa...@intel.com; > erik.g.carri...@intel.com; Phil Yang <phil.y...@arm.com>; nd <n...@arm.com> > Subject: [PATCH v4 0/4] generic rte atomic APIs deprecate proposal > > 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 > > -- > 2.7.4
