From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by dpdk.org (Postfix) with ESMTP id CCDFF4CAB; Fri, 9 Nov 2018 12:43:06 +0100 (CET) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2181B80D; Fri, 9 Nov 2018 03:43:06 -0800 (PST) Received: from net-arm-c2400.shanghai.arm.com (net-arm-c2400.shanghai.arm.com [10.169.40.108]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 5EA5D3F718; Fri, 9 Nov 2018 03:43:04 -0800 (PST) From: Gavin Hu To: dev@dpdk.org Cc: thomas@monjalon.net, stephen@networkplumber.org, olivier.matz@6wind.com, chaozhu@linux.vnet.ibm.com, bruce.richardson@intel.com, konstantin.ananyev@intel.com, jerin.jacob@caviumnetworks.com, Honnappa.Nagarahalli@arm.com, gavin.hu@arm.com, stable@dpdk.org Date: Fri, 9 Nov 2018 19:42:47 +0800 Message-Id: <1541763767-7399-3-git-send-email-gavin.hu@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1541763767-7399-1-git-send-email-gavin.hu@arm.com> References: <1541763767-7399-1-git-send-email-gavin.hu@arm.com> Subject: [dpdk-dev] [PATCH v1 2/2] ring: relaxed ordering for load and store the head 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: , X-List-Received-Date: Fri, 09 Nov 2018 11:43:07 -0000 When calling __atomic_compare_exchange_n, use relaxed ordering for the success case, as multiple producers/consumers do not release updates to each other so no need for acquire or release ordering. Because the thread fence in place, ordering for the first iteration can be relaxed. Run the ring perf test on the following testbed: HW: ThunderX2 B0 CPU CN9975 v2.0, 2 sockets, 28core,4 threads/core,2.5GHz OS: Ubuntu 16.04.5 LTS, Kernel: 4.15.0-36-generic DPDK: 18.08, Configuration: arm64-armv8a-linuxapp-gcc gcc: 8.1.0 $sudo ./test/test/test -l 16-19,44-47,72-75,100-103 -n 4 \ --socket-mem=1024 -- -i Without the patch: *** Testing using two physical cores *** SP/SC bulk enq/dequeue (size: 8): 5.75 MP/MC bulk enq/dequeue (size: 8): 10.18 SP/SC bulk enq/dequeue (size: 32): 1.80 MP/MC bulk enq/dequeue (size: 32): 2.34 With the patch: *** Testing using two physical cores *** SP/SC bulk enq/dequeue (size: 8): 5.59 MP/MC bulk enq/dequeue (size: 8): 10.54 SP/SC bulk enq/dequeue (size: 32): 1.73 MP/MC bulk enq/dequeue (size: 32): 2.38 No significant improvement, nor regression was seen,as the optimisation is not at the critical path. Fixes: 39368ebfc6 ("ring: introduce C11 memory model barrier option") Cc: stable@dpdk.org Signed-off-by: Gavin Hu Reviewed-by: Honnappa Nagarahalli Reviewed-by: Steve Capper Reviewed-by: Ola Liljedahl --- lib/librte_ring/rte_ring_c11_mem.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/lib/librte_ring/rte_ring_c11_mem.h b/lib/librte_ring/rte_ring_c11_mem.h index dc49a99..0fb73a3 100644 --- a/lib/librte_ring/rte_ring_c11_mem.h +++ b/lib/librte_ring/rte_ring_c11_mem.h @@ -61,7 +61,7 @@ __rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp, unsigned int max = n; int success; - *old_head = __atomic_load_n(&r->prod.head, __ATOMIC_ACQUIRE); + *old_head = __atomic_load_n(&r->prod.head, __ATOMIC_RELAXED); do { /* Reset n to the initial burst count */ n = max; @@ -97,7 +97,7 @@ __rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp, /* on failure, *old_head is updated */ success = __atomic_compare_exchange_n(&r->prod.head, old_head, *new_head, - 0, __ATOMIC_ACQUIRE, + 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED); } while (unlikely(success == 0)); return n; @@ -137,7 +137,7 @@ __rte_ring_move_cons_head(struct rte_ring *r, int is_sc, int success; /* move cons.head atomically */ - *old_head = __atomic_load_n(&r->cons.head, __ATOMIC_ACQUIRE); + *old_head = __atomic_load_n(&r->cons.head, __ATOMIC_RELAXED); do { /* Restore n as it may change every loop */ n = max; @@ -172,7 +172,7 @@ __rte_ring_move_cons_head(struct rte_ring *r, int is_sc, /* on failure, *old_head will be updated */ success = __atomic_compare_exchange_n(&r->cons.head, old_head, *new_head, - 0, __ATOMIC_ACQUIRE, + 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED); } while (unlikely(success == 0)); return n; -- 2.7.4