[dpdk-dev] [memnic PATCH v2 5/7] pmd: packet receiving optimization with prefetch
Hiroshi Shimamoto
h-shimamoto at ct.jp.nec.com
Tue Sep 30 13:14:12 CEST 2014
From: Hiroshi Shimamoto <h-shimamoto at ct.jp.nec.com>
Prefetch the next packet area to reduce memory stall cycles.
Prefetching the next packet area could hide memory stall, because the next
area will be accessed just after processing the current receive operations.
We can see performance improvements with memnic-tester.
Using Xeon E5-2697 v2 @ 2.70GHz, 4 vCPU.
size | before | after
64 | 4.59Mpps | 5.54Mpps
128 | 4.87Mpps | 5.46Mpps
256 | 4.72Mpps | 5.21Mpps
512 | 4.41Mpps | 4.50Mpps
1024 | 3.64Mpps | 3.71Mpps
1280 | 3.15Mpps | 3.21Mpps
1518 | 2.87Mpps | 2.92Mpps
Signed-off-by: Hiroshi Shimamoto <h-shimamoto at ct.jp.nec.com>
Reviewed-by: Hayato Momma <h-momma at ce.jp.nec.com>
---
pmd/pmd_memnic.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/pmd/pmd_memnic.c b/pmd/pmd_memnic.c
index 0783440..7fc3093 100644
--- a/pmd/pmd_memnic.c
+++ b/pmd/pmd_memnic.c
@@ -286,7 +286,7 @@ static uint16_t memnic_recv_pkts(void *rx_queue,
uint16_t nr;
uint64_t pkts, bytes, errs;
uint32_t framesz = adapter->framesz;
- int idx;
+ int idx, next;
struct rte_eth_stats *st = &adapter->stats[rte_lcore_id()];
if (!adapter->nic->hdr.valid)
@@ -298,6 +298,11 @@ static uint16_t memnic_recv_pkts(void *rx_queue,
p = &data->packets[idx];
if (p->status != MEMNIC_PKT_ST_FILLED)
break;
+ /* prefetch the next area */
+ next = idx;
+ if (++next >= MEMNIC_NR_PACKET)
+ next = 0;
+ rte_prefetch0(&data->packets[next]);
if (p->len > framesz) {
errs++;
goto drop;
@@ -318,9 +323,7 @@ static uint16_t memnic_recv_pkts(void *rx_queue,
drop:
rte_compiler_barrier();
p->status = MEMNIC_PKT_ST_FREE;
-
- if (++idx >= MEMNIC_NR_PACKET)
- idx = 0;
+ idx = next;
}
adapter->up_idx = idx;
--
1.8.3.1
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