[PATCH net-next 1/3] sunvnet: Do not ask for an ACK for every dring transmit
From: Sowmini Varadhan <hidden>
Date: 2014-08-12 14:27:30
Subsystem:
networking drivers, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
No need to ask for an ack with every vnet_start_xmit()- the single ACK with DRING_STOPPED is sufficient for the protocol, and we free the sk_buff in vnet_start_xmit itself, so we dont need an ACK back. Signed-off-by: Sowmini Varadhan <redacted> Acked-by: Raghuram Kothakota <redacted> --- drivers/net/ethernet/sun/sunvnet.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c
index d813bfb..b489dd0 100644
--- a/drivers/net/ethernet/sun/sunvnet.c
+++ b/drivers/net/ethernet/sun/sunvnet.c@@ -691,7 +691,15 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev) memset(tx_buf+VNET_PACKET_SKIP+skb->len, 0, len - skb->len); } - d->hdr.ack = VIO_ACK_ENABLE; + /* We don't rely on the ACKs to free the skb in vnet_start_xmit(), + * thus it is safe to not set VIO_ACK_ENABLE for each transmission: + * the protocol itself does not require it as long as the peer + * sends a VIO_SUBTYPE_ACK for VIO_DRING_STOPPED. + * + * An ACK for every packet in the ring is expensive as the + * sending of LDC messages is slow and affects performance. + */ + d->hdr.ack = VIO_ACK_DISABLE; d->size = len; d->ncookies = port->tx_bufs[dr->prod].ncookies; for (i = 0; i < d->ncookies; i++)
--
1.8.4.2