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From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
To: "dev@dpdk.org" <dev@dpdk.org>
Cc: Hayato Momma <h-momma@ce.jp.nec.com>
Subject: [dpdk-dev] [memnic PATCH 4/7] pmd: use compiler barrier
Date: Thu, 11 Sep 2014 07:48:31 +0000
Message-ID: <7F861DC0615E0C47A872E6F3C5FCDDBD011A9934@BPXM14GP.gisp.nec.co.jp> (raw)

From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>

x86 can keep store ordering with standard operations.

Using memory barrier is much expensive in main packet processing loop.
Removing this improves xmit/recv packet performance.

We can see performance improvements with memnic-tester.
Using Xeon E5-2697 v2 @ 2.70GHz, 4 vCPU.
 size |  before  |  after
   64 | 4.18Mpps | 4.59Mpps
  128 | 3.85Mpps | 4.87Mpps
  256 | 4.01Mpps | 4.72Mpps
  512 | 3.52Mpps | 4.41Mpps
 1024 | 3.18Mpps | 3.64Mpps
 1280 | 2.86Mpps | 3.15Mpps
 1518 | 2.59Mpps | 2.87Mpps

Note: we have to take care if we use temporal cache.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Reviewed-by: Hayato Momma <h-momma@ce.jp.nec.com>
---
 pmd/pmd_memnic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pmd/pmd_memnic.c b/pmd/pmd_memnic.c
index 8341da7..c22a14d 100644
--- a/pmd/pmd_memnic.c
+++ b/pmd/pmd_memnic.c
@@ -316,7 +316,7 @@ static uint16_t memnic_recv_pkts(void *rx_queue,
 		bytes += p->len;
 
 drop:
-		rte_mb();
+		rte_compiler_barrier();
 		p->status = MEMNIC_PKT_ST_FREE;
 
 		if (++idx >= MEMNIC_NR_PACKET)
@@ -403,7 +403,7 @@ retry:
 		pkts++;
 		bytes += pkt_len;
 
-		rte_mb();
+		rte_compiler_barrier();
 		p->status = MEMNIC_PKT_ST_FILLED;
 
 		rte_pktmbuf_free(tx_pkts[nr]);
-- 
1.8.3.1

             reply	other threads:[~2014-09-11  7:52 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-11  7:48 Hiroshi Shimamoto [this message]
2014-09-24 15:18 ` Thomas Monjalon
2014-09-25  0:35   ` Hiroshi Shimamoto

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