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From: Gavin Hu <gavin.hu@arm.com>
To: dev@dpdk.org
Cc: nd@arm.com, thomas@monjalon.net, jerinj@marvell.com,
	pbhagavatula@marvell.com, Honnappa.Nagarahalli@arm.com,
	qi.z.zhang@intel.com, bruce.richardson@intel.com,
	stable@dpdk.org
Subject: [dpdk-stable] [PATCH 1/2] net/i40e: desc loading is unnecessarily ordered for aarch64
Date: Tue, 13 Aug 2019 18:43:30 +0800	[thread overview]
Message-ID: <1565693011-33998-2-git-send-email-gavin.hu@arm.com> (raw)
In-Reply-To: <1565693011-33998-1-git-send-email-gavin.hu@arm.com>

For x86, the descriptors needs to be loaded in order, so in between two
descriptors loading, there is a compiler barrier in place.[1]
For aarch64, a patch [2] is in place to survive with discontinuous DD bits,
the barriers can be removed to take full advantage of out-of-order
execution.

50% performance gain in the RFC2544 NDR test was measured on ThunderX2.
12.50% performan gain in the RFC2544 NDR test was measured on Ampere
eMAG80 platform.

[1] http://inbox.dpdk.org/users/039ED4275CED7440929022BC67E7061153D71548@
SHSMSX105.ccr.corp.intel.com/
[2] https://mails.dpdk.org/archives/stable/2017-October/003324.html

Fixes: ae0eb310f253 ("net/i40e: implement vector PMD for ARM")
Cc: stable@dpdk.org

Signed-off-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Steve Capper <steve.capper@arm.com>
---
 drivers/net/i40e/i40e_rxtx_vec_neon.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/i40e/i40e_rxtx_vec_neon.c b/drivers/net/i40e/i40e_rxtx_vec_neon.c
index 83572ef..5555e9b 100644
--- a/drivers/net/i40e/i40e_rxtx_vec_neon.c
+++ b/drivers/net/i40e/i40e_rxtx_vec_neon.c
@@ -285,7 +285,6 @@ _recv_raw_pkts_vec(struct i40e_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 		/* Read desc statuses backwards to avoid race condition */
 		/* A.1 load 4 pkts desc */
 		descs[3] =  vld1q_u64((uint64_t *)(rxdp + 3));
-		rte_rmb();
 
 		/* B.2 copy 2 mbuf point into rx_pkts  */
 		vst1q_u64((uint64_t *)&rx_pkts[pos], mbp1);
-- 
2.7.4


       reply	other threads:[~2019-08-13 10:44 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1565693011-33998-1-git-send-email-gavin.hu@arm.com>
2019-08-13 10:43 ` Gavin Hu [this message]
2019-08-28 22:09   ` Honnappa Nagarahalli
2019-08-30  8:33     ` Gavin Hu (Arm Technology China)
2019-08-13 10:43 ` [dpdk-stable] [PATCH 2/2] net/i40e: remove compiler barrier " Gavin Hu
2019-08-28 22:48   ` Honnappa Nagarahalli
2019-08-30  8:51     ` Gavin Hu (Arm Technology China)

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