From: Sven Van Asbroeck <thesve...@gmail.com>
To support jumbo frames, each rx ring dma buffer is 9K in size.
But the chip only stores a single frame per dma buffer.
When the chip is working with the default 1500 byte MTU, a 9K
dma buffer goes from chip -> cpu per 1500 byte frame. This means
that to get 1G/s ethernet bandwidth, we need 6G/s PCIe bandwidth !
Fix by limiting the rx ring dma buffer size to the current MTU
size.
Tested with iperf3 on a freescale imx6 + lan7430, both sides
set to mtu 1500 bytes.
Before:
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-20.00 sec 483 MBytes 203 Mbits/sec 0
After:
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-20.00 sec 1.15 GBytes 496 Mbits/sec 0
And with both sides set to MTU 9000 bytes:
Before:
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-20.00 sec 1.87 GBytes 803 Mbits/sec 27
After:
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-20.00 sec 1.98 GBytes 849 Mbits/sec 0
Tested-by: Sven Van Asbroeck <thesve...@gmail.com> # lan7430
Signed-off-by: Sven Van Asbroeck <thesve...@gmail.com>
---
Tree: git://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git # 905b2032fa42
To: Bryan Whitehead <bryan.whiteh...@microchip.com>
To: Microchip Linux Driver Support <unglinuxdri...@microchip.com>
To: "David S. Miller" <da...@davemloft.net>
To: Jakub Kicinski <k...@kernel.org>
Cc: Andrew Lunn <and...@lunn.ch>
Cc: net...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
drivers/net/ethernet/microchip/lan743x_main.c | 21 ++++++++++++-------
1 file changed, 13 insertions(+), 8 deletions(-)
diff --git a/drivers/net/ethernet/microchip/lan743x_main.c
b/drivers/net/ethernet/microchip/lan743x_main.c
index ebb5e0bc516b..2bded1c46784 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -1957,11 +1957,11 @@ static int lan743x_rx_next_index(struct lan743x_rx *rx,
int index)
static struct sk_buff *lan743x_rx_allocate_skb(struct lan743x_rx *rx)
{
- int length = 0;
+ struct net_device *netdev = rx->adapter->netdev;
- length = (LAN743X_MAX_FRAME_SIZE + ETH_HLEN + 4 + RX_HEAD_PADDING);
- return __netdev_alloc_skb(rx->adapter->netdev,
- length, GFP_ATOMIC | GFP_DMA);
+ return __netdev_alloc_skb(netdev,
+ netdev->mtu + ETH_HLEN + 4 + RX_HEAD_PADDING,
+ GFP_ATOMIC | GFP_DMA);
}
static int lan743x_rx_init_ring_element(struct lan743x_rx *rx, int index,
@@ -1969,9 +1969,10 @@ static int lan743x_rx_init_ring_element(struct
lan743x_rx *rx, int index,
{
struct lan743x_rx_buffer_info *buffer_info;
struct lan743x_rx_descriptor *descriptor;
- int length = 0;
+ struct net_device *netdev = rx->adapter->netdev;
+ int length;
- length = (LAN743X_MAX_FRAME_SIZE + ETH_HLEN + 4 + RX_HEAD_PADDING);
+ length = netdev->mtu + ETH_HLEN + 4 + RX_HEAD_PADDING;
descriptor = &rx->ring_cpu_ptr[index];
buffer_info = &rx->buffer_info[index];
buffer_info->skb = skb;
@@ -2157,8 +2158,8 @@ static int lan743x_rx_process_packet(struct lan743x_rx
*rx)
int index = first_index;
/* multi buffer packet not supported */
- /* this should not happen since
- * buffers are allocated to be at least jumbo size
+ /* this should not happen since buffers are allocated
+ * to be at least the mtu size configured in the mac.
*/
/* clean up buffers */
@@ -2632,9 +2633,13 @@ static int lan743x_netdev_change_mtu(struct net_device
*netdev, int new_mtu)
struct lan743x_adapter *adapter = netdev_priv(netdev);
int ret = 0;
+ if (netif_running(netdev))
+ return -EBUSY;
+
ret = lan743x_mac_set_mtu(adapter, new_mtu);
if (!ret)
netdev->mtu = new_mtu;
+
return ret;
}
--
2.17.1
