[ovs-dev] [PATCH v2 ] flow: save "vlan_hdrs" memset for untagged traffic

Yanqin Wei Yanqin.Wei at arm.com
Thu Aug 22 10:09:50 UTC 2019


For untagged traffic, it is unnecessary to clear vlan_hdrs as it costs 32B
memset. So the patch improves it by postponing to clear vlan_hdrs until
ethtype check. It can benefit both untagged and single-tagged traffic. From
testing, it does not impact performance of dual-tagged traffic.

Reviewed-by: Gavin Hu <Gavin.Hu at arm.com>
Signed-off-by: Yanqin Wei <Yanqin.Wei at arm.com>
---
 lib/flow.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/flow.c b/lib/flow.c
index 1b21f51..4d895e5 100644
--- a/lib/flow.c
+++ b/lib/flow.c
@@ -343,7 +343,6 @@ parse_vlan(const void **datap, size_t *sizep, union flow_vlan_hdr *vlan_hdrs)
 {
     const ovs_be16 *eth_type;
 
-    memset(vlan_hdrs, 0, sizeof(union flow_vlan_hdr) * FLOW_MAX_VLAN_HEADERS);
     data_pull(datap, sizep, ETH_ADDR_LEN * 2);
 
     eth_type = *datap;
@@ -354,6 +353,7 @@ parse_vlan(const void **datap, size_t *sizep, union flow_vlan_hdr *vlan_hdrs)
             break;
         }
 
+        memset(vlan_hdrs + n, 0, sizeof(union flow_vlan_hdr));
         const ovs_16aligned_be32 *qp = data_pull(datap, sizep, sizeof *qp);
         vlan_hdrs[n].qtag = get_16aligned_be32(qp);
         vlan_hdrs[n].tci |= htons(VLAN_CFI);
-- 
2.7.4



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