[dpdk-dev] [memnic PATCH 7/7] pmd: split calling mbuf free

[Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>]

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

In rte_pktmbuf_free(), there might be cache miss/memory stall issue.
In small packet case, it could harm the performance.

>From the result of memnic-tester, in less than 1024 frame size the
performance could be improved.

Using Xeon E5-2697 v2 @ 2.70GHz, 4 vCPU.
 size |  before  |  after
   64 | 5.55Mpps | 5.83Mpps
  128 | 5.44Mpps | 5.71Mpps
  256 | 5.22Mpps | 5.40Mpps
  512 | 4.52Mpps | 4.64Mpps
 1024 | 3.73Mpps | 3.68Mpps
 1280 | 3.22Mpps | 3.17Mpps
 1518 | 2.93Mpps | 2.90Mpps

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 | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/pmd/pmd_memnic.c b/pmd/pmd_memnic.c
index cc0ae25..1db065f 100644
--- a/pmd/pmd_memnic.c
+++ b/pmd/pmd_memnic.c
@@ -344,7 +344,7 @@ static uint16_t memnic_xmit_pkts(void *tx_queue,
 	struct memnic_adapter *adapter = q->adapter;
 	struct memnic_data *data = &adapter->nic->down;
 	struct memnic_packet *p;
-	uint16_t nr;
+	uint16_t i, nr;
 	int idx;
 	struct rte_eth_stats *st = &adapter->stats[rte_lcore_id()];
 	uint64_t pkts, bytes, errs;
@@ -408,9 +408,9 @@ retry:
 
 		rte_compiler_barrier();
 		p->status = MEMNIC_PKT_ST_FILLED;
-
-		rte_pktmbuf_free(tx_pkts[nr]);
 	}
+	for (i = 0; i < nr; i++)
+		rte_pktmbuf_free(tx_pkts[i]);
 
 	/* stats */
 	st->opackets += pkts;
-- 
1.8.3.1