linux-kernel - Re: [Intel-wired-lan] [PATCH iwl-next v3 1/1] igc: Avoid unnecessary link down event in XDP_SETUP

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Message-ID: <8b993e58-290a-f852-2f53-dd14e7be0cce@intel.com>
Date: Mon, 23 Dec 2024 15:52:58 +0200
From: Avigail Dahan <Avigailx.dahan@...el.com>
To: Song Yoong Siang <yoong.siang.song@...el.com>, Alexei Starovoitov
	<ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, "David S . Miller"
	<davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, "Jesper Dangaard
 Brouer" <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, "Tony
 Nguyen" <anthony.l.nguyen@...el.com>, Przemek Kitszel
	<przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "Eric
 Dumazet" <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, "Vinicius
 Costa Gomes" <vinicius.gomes@...el.com>, Maciej Fijalkowski
	<maciej.fijalkowski@...el.com>, Paul Menzel <pmenzel@...gen.mpg.de>
CC: <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>
Subject: Re: [Intel-wired-lan] [PATCH iwl-next v3 1/1] igc: Avoid unnecessary
 link down event in XDP_SETUP_PROG process



On 16/12/2024 9:38, Song Yoong Siang wrote:
> The igc_close()/igc_open() functions are too drastic for installing a new
> XDP prog because they cause undesirable link down event and device reset.
> 
> To avoid delays in Ethernet traffic, improve the XDP_SETUP_PROG process by
> using the same sequence as igc_xdp_setup_pool(), which performs only the
> necessary steps, as follows:
>   1. stop the traffic and clean buffer
>   2. stop NAPI
>   3. install the XDP program
>   4. resume NAPI
>   5. allocate buffer and resume the traffic
> 
> This patch has been tested using the 'ip link set xdpdrv' command to attach
> a simple XDP prog that always returns XDP_PASS.
> 
> Before this patch, attaching xdp program will cause ptp4l to lose sync for
> few seconds, as shown in ptp4l log below:
>    ptp4l[198.082]: rms    4 max    8 freq   +906 +/-   2 delay    12 +/-   0
>    ptp4l[199.082]: rms    3 max    4 freq   +906 +/-   3 delay    12 +/-   0
>    ptp4l[199.536]: port 1 (enp2s0): link down
>    ptp4l[199.536]: port 1 (enp2s0): SLAVE to FAULTY on FAULT_DETECTED (FT_UNSPECIFIED)
>    ptp4l[199.600]: selected local clock 22abbc.fffe.bb1234 as best master
>    ptp4l[199.600]: port 1 (enp2s0): assuming the grand master role
>    ptp4l[199.600]: port 1 (enp2s0): master state recommended in slave only mode
>    ptp4l[199.600]: port 1 (enp2s0): defaultDS.priority1 probably misconfigured
>    ptp4l[202.266]: port 1 (enp2s0): link up
>    ptp4l[202.300]: port 1 (enp2s0): FAULTY to LISTENING on INIT_COMPLETE
>    ptp4l[205.558]: port 1 (enp2s0): new foreign master 44abbc.fffe.bb2144-1
>    ptp4l[207.558]: selected best master clock 44abbc.fffe.bb2144
>    ptp4l[207.559]: port 1 (enp2s0): LISTENING to UNCALIBRATED on RS_SLAVE
>    ptp4l[208.308]: port 1 (enp2s0): UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
>    ptp4l[208.933]: rms  742 max 1303 freq   -195 +/- 682 delay    12 +/-   0
>    ptp4l[209.933]: rms  178 max  274 freq   +387 +/- 243 delay    12 +/-   0
> 
> After this patch, attaching xdp program no longer cause ptp4l to lose sync,
> as shown in ptp4l log below:
>    ptp4l[201.183]: rms    1 max    3 freq   +959 +/-   1 delay     8 +/-   0
>    ptp4l[202.183]: rms    1 max    3 freq   +961 +/-   2 delay     8 +/-   0
>    ptp4l[203.183]: rms    2 max    3 freq   +958 +/-   2 delay     8 +/-   0
>    ptp4l[204.183]: rms    3 max    5 freq   +961 +/-   3 delay     8 +/-   0
>    ptp4l[205.183]: rms    2 max    4 freq   +964 +/-   3 delay     8 +/-   0
> 
> Besides, before this patch, attaching xdp program will causes flood ping to
> lose 10 packets, as shown in ping statistics below:
>    --- 169.254.1.2 ping statistics ---
>    100000 packets transmitted, 99990 received, +6 errors, 0.01% packet loss, time 34001ms
>    rtt min/avg/max/mdev = 0.028/0.301/3104.360/13.838 ms, pipe 10, ipg/ewma 0.340/0.243 ms
> 
> After this patch, attaching xdp program no longer cause flood ping to loss
> any packets, as shown in ping statistics below:
>    --- 169.254.1.2 ping statistics ---
>    100000 packets transmitted, 100000 received, 0% packet loss, time 32326ms
>    rtt min/avg/max/mdev = 0.027/0.231/19.589/0.155 ms, pipe 2, ipg/ewma 0.323/0.322 ms
> 
> On the other hand, this patch has been tested with tools/testing/selftests/
> bpf/xdp_hw_metadata app to make sure AF_XDP zero-copy is working fine with
> XDP Tx and Rx metadata. Below is the result of last packet after received
> 10000 UDP packets with interval 1 ms:
>    poll: 1 (0) skip=0 fail=0 redir=10000
>    xsk_ring_cons__peek: 1
>    0x55881c7ef7a8: rx_desc[9999]->addr=8f110 addr=8f110 comp_addr=8f110 EoP
>    rx_hash: 0xFB9BB6A3 with RSS type:0x1
>    HW RX-time:   1733923136269470866 (sec:1733923136.2695) delta to User RX-time sec:0.0000 (43.280 usec)
>    XDP RX-time:   1733923136269482482 (sec:1733923136.2695) delta to User RX-time sec:0.0000 (31.664 usec)
>    No rx_vlan_tci or rx_vlan_proto, err=-95
>    0x55881c7ef7a8: ping-pong with csum=ab19 (want 315b) csum_start=34 csum_offset=6
>    0x55881c7ef7a8: complete tx idx=9999 addr=f010
>    HW TX-complete-time:   1733923136269591637 (sec:1733923136.2696) delta to User TX-complete-time sec:0.0001 (108.571 usec)
>    XDP RX-time:   1733923136269482482 (sec:1733923136.2695) delta to User TX-complete-time sec:0.0002 (217.726 usec)
>    HW RX-time:   1733923136269470866 (sec:1733923136.2695) delta to HW TX-complete-time sec:0.0001 (120.771 usec)
>    0x55881c7ef7a8: complete rx idx=10127 addr=8f110
> 
> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
> ---
> V2: https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20241211134532.3489335-1-yoong.siang.song@intel.com/
> V1: https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20241204120233.3148482-1-yoong.siang.song@intel.com/
> 
> V3 changelog:
>   - Change commit title to be more specific. (Paul)
>   - Use unsigned int, instead of int, for array elements. (Paul)
>   - Fix grammar mistakes on commit message. (Paul)
>   - Explain why igc_close()/igc_open() are not needed in commit message. (Paul)
> V2 changelog:
>   - shows some examples of problem in commit message. (Vinicius)
>   - igc_close()/igc_open() are too big a hammer for installing a new XDP
>     program. Only do we we really need. (Vinicius)
> ---
>   drivers/net/ethernet/intel/igc/igc_xdp.c | 19 +++++++++++++++----
>   1 file changed, 15 insertions(+), 4 deletions(-)
>Tested-by: Avigail Dahan <avigailx.dahan@...el.com>