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>
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 2953b2a..18fe20d 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -2660,6 +2660,7 @@
sprintf(pkt_dev->result, "No memory");
return NULL;
}
+ prefetchw(skb->data);
skb_reserve(skb, datalen);
@@ -3007,6 +3008,7 @@
sprintf(pkt_dev->result, "No memory");
return NULL;
}
+ prefetchw(skb->data);
skb_reserve(skb, 16);