lkml.org 
[lkml]   [2022]   [Mar]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH net-next 0/5] net: lan966x: Add support for FDMA
Am 2022-03-18 13:10, schrieb Horatiu Vultur:
> The 03/18/2022 12:07, Michael Walle wrote:
>> > Currently when injecting or extracting a frame from CPU, the frame
>> > is given to the HW each word at a time. There is another way to
>> > inject/extract frames from CPU using FDMA(Frame Direct Memory Access).
>> > In this way the entire frame is given to the HW. This improves both
>> > RX and TX bitrate.
>>
>> I wanted to test this. ping and such works fine and I'm also
>> seeing fdma interrupts.
>
> Thanks for testing this also on your board.
>
>> But as soon as I try iperf3 I get a skb_panic
>> (due to frame size?). Hope that splash below helps.
>
> I have not seen this issue. But it looks like it is a problem that
> there
> is no more space to add the FCS.
> Can you tell me how you run iperf3 so I can also try it?

oh, I forgot to include the commandline.

# on the remote computer
$ iperf3 --version
iperf 3.6 (cJSON 1.5.2)
Linux eddie01 4.19.0-18-686-pae #1 SMP Debian 4.19.208-1 (2021-09-29)
i686
Optional features available: CPU affinity setting, IPv6 flow label,
SCTP, TCP congestion algorithm setting, sendfile / zerocopy, socket
pacing, authentication
$ iperf3 -s

# on the board
$ iperf3 --version
iperf 3.10.1 (cJSON 1.7.13)
Linux buildroot 5.17.0-rc8-next-20220316-00058-gc6cb0628f2a6-dirty #385
SMP Fri Mar 18 13:34:26 CET 2022 armv7l
Optional features available: CPU affinity setting, IPv6 flow label, TCP
congestion algorithm setting, sendfile / zerocopy, socket pacing, bind
to device, support IPv4 don't fragment
$ iperf3 -c eddie01

> Also I have a small diff that might fix the issue:
> ---
> --- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> @@ -534,6 +534,8 @@ int lan966x_fdma_xmit(struct sk_buff *skb, __be32
> *ifh, struct net_device *dev)
> struct lan966x_tx_dcb *next_dcb, *dcb;
> struct lan966x_tx *tx = &lan966x->tx;
> struct lan966x_db *next_db;
> + int needed_headroom;
> + int needed_tailroom;
> dma_addr_t dma_addr;
> int next_to_use;
> int err;
> @@ -554,10 +556,11 @@ int lan966x_fdma_xmit(struct sk_buff *skb,
> __be32 *ifh, struct net_device *dev)
>
> /* skb processing */
> skb_tx_timestamp(skb);

btw. skb_tx_timestamp() should be as close to the handover
of the frame to the hardware as possible, no?

> - if (skb_headroom(skb) < IFH_LEN * sizeof(u32)) {
> - err = pskb_expand_head(skb,
> - IFH_LEN * sizeof(u32) -
> skb_headroom(skb),
> - 0, GFP_ATOMIC);
> + needed_headroom = max_t(int, IFH_LEN * sizeof(u32) -
> skb_headroom(skb), 0);
> + needed_tailroom = max_t(int, ETH_FCS_LEN - skb_tailroom(skb),
> 0);
> + if (needed_headroom || needed_tailroom) {
> + err = pskb_expand_head(skb, needed_headroom,
> needed_tailroom,
> + GFP_ATOMIC);
> if (unlikely(err)) {
> dev->stats.tx_dropped++;
> err = NETDEV_TX_OK;

Indeed this will fix the issue:

# iperf3 -c eddie01
Connecting to host eddie01, port 5201
[ 5] local 10.0.1.143 port 55342 connected to 10.0.1.42 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.01 sec 43.8 MBytes 364 Mbits/sec 0 245 KBytes
[ 5] 1.01-2.02 sec 43.8 MBytes 364 Mbits/sec 0 246 KBytes
[ 5] 2.02-3.03 sec 43.8 MBytes 364 Mbits/sec 0 259 KBytes

# iperf3 -R -c eddie01
Connecting to host eddie01, port 5201
Reverse mode, remote host eddie01 is sending
[ 5] local 10.0.1.143 port 55346 connected to 10.0.1.42 port 5201
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 28.6 MBytes 240 Mbits/sec
[ 5] 1.00-2.00 sec 28.9 MBytes 242 Mbits/sec
[ 5] 2.00-3.00 sec 28.7 MBytes 241 Mbits/sec

-michael

\
 
 \ /
  Last update: 2022-03-18 13:43    [W:0.062 / U:0.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site