Commit a8d764b9 authored Dec 08, 2010 by Junchang Wang Committed by David S. Miller Dec 10, 2010

pktgen: adding prefetchw() call



We know for sure pktgen is going to write skb->data right after
*_alloc_skb, causing unnecessary cache misses.

Idea is to add a prefetchw() call to prefetch the first cache line
indicated by skb->data. On systems with Adjacent Cache Line Prefetch,
it's probably two cache lines are prefetched.

With this patch, pktgen on Intel SR1625 server with two E5530
quad-core processors and a single ixgbe-based NIC went from 8.63Mpps
to 9.03Mpps, with 4.6% improvement.

Signed-off-by: Junchang Wang <junchangwang@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 4afb7527

net/core/pktgen.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -2660,6 +2660,7 @@ static struct sk_buff fill_packet_ipv4(struct net_device odev,
		sprintf(pkt_dev->result, "No memory");
		return NULL;
		}
		prefetchw(skb->data);

		skb_reserve(skb, datalen);

		@@ -3007,6 +3008,7 @@ static struct sk_buff fill_packet_ipv6(struct net_device odev,
		sprintf(pkt_dev->result, "No memory");
		return NULL;
		}
		prefetchw(skb->data);

		skb_reserve(skb, 16);