* [dpdk-dev] [memnic PATCH v2 4/7] pmd: use compiler barrier
@ 2014-09-30 11:13 Hiroshi Shimamoto
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From: Hiroshi Shimamoto @ 2014-09-30 11:13 UTC (permalink / raw)
To: dev; +Cc: Hayato Momma
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 non-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 872f3c4..0783440 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
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