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Message-ID: <Z6UNt2GatiYYdZIW@boxer>
Date: Thu, 6 Feb 2025 20:29:59 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Song Yoong Siang <yoong.siang.song@...el.com>
CC: "David S . Miller" <davem@...emloft.net>, Eric Dumazet
<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>, Simon Horman <horms@...nel.org>, Willem de Bruijn
<willemb@...gle.com>, Florian Bezdeka <florian.bezdeka@...mens.com>, "Donald
Hunter" <donald.hunter@...il.com>, Jonathan Corbet <corbet@....net>, "Bjorn
Topel" <bjorn@...nel.org>, Magnus Karlsson <magnus.karlsson@...el.com>,
Jonathan Lemon <jonathan.lemon@...il.com>, Andrew Lunn
<andrew+netdev@...n.ch>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
<daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, "John
Fastabend" <john.fastabend@...il.com>, Joe Damato <jdamato@...tly.com>,
Stanislav Fomichev <sdf@...ichev.me>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
Mina Almasry <almasrymina@...gle.com>, Daniel Jurgens <danielj@...dia.com>,
Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>,
Mykola Lysenko <mykolal@...com>, Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, KP Singh
<kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>, Jiri Olsa
<jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>, Alexandre Torgue
<alexandre.torgue@...s.st.com>, Jose Abreu <joabreu@...opsys.com>, "Maxime
Coquelin" <mcoquelin.stm32@...il.com>, Tony Nguyen
<anthony.l.nguyen@...el.com>, Przemek Kitszel <przemyslaw.kitszel@...el.com>,
Faizal Rahim <faizal.abdul.rahim@...ux.intel.com>, Choong Yong Liang
<yong.liang.choong@...ux.intel.com>, Bouska Zdenek
<zdenek.bouska@...mens.com>, <netdev@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<bpf@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
<linux-stm32@...md-mailman.stormreply.com>,
<linux-arm-kernel@...ts.infradead.org>, <intel-wired-lan@...ts.osuosl.org>,
<xdp-hints@...-project.net>
Subject: Re: [PATCH bpf-next v9 5/5] igc: Add launch time support to XDP ZC
On Thu, Feb 06, 2025 at 02:04:08PM +0800, Song Yoong Siang wrote:
> Enable Launch Time Control (LTC) support for XDP zero copy via XDP Tx
> metadata framework.
>
> This patch has been tested with tools/testing/selftests/bpf/xdp_hw_metadata
> on Intel I225-LM Ethernet controller. Below are the test steps and result.
>
> Test 1: Send a single packet with the launch time set to 1 s in the future.
>
> Test steps:
> 1. On the DUT, start the xdp_hw_metadata selftest application:
> $ sudo ./xdp_hw_metadata enp2s0 -l 1000000000 -L 1
>
> 2. On the Link Partner, send a UDP packet with VLAN priority 1 to port 9091
> of the DUT.
>
> Result:
> When the launch time is set to 1 s in the future, the delta between the
> launch time and the transmit hardware timestamp is 0.016 us, as shown in
> printout of the xdp_hw_metadata application below.
> 0x562ff5dc8880: rx_desc[4]->addr=84110 addr=84110 comp_addr=84110 EoP
> rx_hash: 0xE343384 with RSS type:0x1
> HW RX-time: 1734578015467548904 (sec:1734578015.4675)
> delta to User RX-time sec:0.0002 (183.103 usec)
> XDP RX-time: 1734578015467651698 (sec:1734578015.4677)
> delta to User RX-time sec:0.0001 (80.309 usec)
> No rx_vlan_tci or rx_vlan_proto, err=-95
> 0x562ff5dc8880: ping-pong with csum=561c (want c7dd)
> csum_start=34 csum_offset=6
> HW RX-time: 1734578015467548904 (sec:1734578015.4675)
> delta to HW Launch-time sec:1.0000 (1000000.000 usec)
> 0x562ff5dc8880: complete tx idx=4 addr=4018
> HW Launch-time: 1734578016467548904 (sec:1734578016.4675)
> delta to HW TX-complete-time sec:0.0000 (0.016 usec)
> HW TX-complete-time: 1734578016467548920 (sec:1734578016.4675)
> delta to User TX-complete-time sec:0.0000
> (32.546 usec)
> XDP RX-time: 1734578015467651698 (sec:1734578015.4677)
> delta to User TX-complete-time sec:0.9999
> (999929.768 usec)
> HW RX-time: 1734578015467548904 (sec:1734578015.4675)
> delta to HW TX-complete-time sec:1.0000 (1000000.016 usec)
> 0x562ff5dc8880: complete rx idx=132 addr=84110
>
> Test 2: Send 1000 packets with a 10 ms interval and the launch time set to
> 500 us in the future.
>
> Test steps:
> 1. On the DUT, start the xdp_hw_metadata selftest application:
> $ sudo chrt -f 99 ./xdp_hw_metadata enp2s0 -l 500000 -L 1 > \
> /dev/shm/result.log
>
> 2. On the Link Partner, send 1000 UDP packets with a 10 ms interval and
> VLAN priority 1 to port 9091 of the DUT.
>
> Result:
> When the launch time is set to 500 us in the future, the average delta
> between the launch time and the transmit hardware timestamp is 0.016 us,
> as shown in the analysis of /dev/shm/result.log below. The XDP launch time
> works correctly in sending 1000 packets continuously.
> Min delta: 0.005 us
> Avr delta: 0.016 us
> Max delta: 0.031 us
> Total packets forwarded: 1000
>
> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
also with one nit. Thanks!
> ---
> drivers/net/ethernet/intel/igc/igc.h | 1 +
> drivers/net/ethernet/intel/igc/igc_main.c | 57 ++++++++++++++++++++++-
> 2 files changed, 56 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
> index b8111ad9a9a8..cd1d7b6c1782 100644
> --- a/drivers/net/ethernet/intel/igc/igc.h
> +++ b/drivers/net/ethernet/intel/igc/igc.h
> @@ -579,6 +579,7 @@ struct igc_metadata_request {
> struct xsk_tx_metadata *meta;
> struct igc_ring *tx_ring;
> u32 cmd_type;
> + u16 used_desc;
> };
>
> struct igc_q_vector {
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 3df608601a4b..f239f744247d 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -2973,9 +2973,44 @@ static u64 igc_xsk_fill_timestamp(void *_priv)
> return *(u64 *)_priv;
> }
>
> +static void igc_xsk_request_launch_time(u64 launch_time, void *_priv)
> +{
> + struct igc_metadata_request *meta_req = _priv;
> + struct igc_ring *tx_ring = meta_req->tx_ring;
> + __le32 launch_time_offset;
> + bool insert_empty = false;
> + bool first_flag = false;
> +
> + if (!tx_ring->launchtime_enable)
> + return;
> +
> + launch_time_offset = igc_tx_launchtime(tx_ring,
> + ns_to_ktime(launch_time),
> + &first_flag, &insert_empty);
> + if (insert_empty) {
> + /* Disregard the launch time request if the required empty frame
> + * fails to be inserted.
> + */
> + if (igc_insert_empty_frame(tx_ring))
> + return;
> +
> + meta_req->tx_buffer =
> + &tx_ring->tx_buffer_info[tx_ring->next_to_use];
> + /* Inserting an empty packet requires two descriptors:
> + * one data descriptor and one context descriptor.
> + */
> + meta_req->used_desc += 2;
tiny nit: you could accumulate the amount of used descs in local variable
and update the igc_metadata_request::used_desc once.
> + }
> +
> + /* Use one context descriptor to specify launch time and first flag. */
> + igc_tx_ctxtdesc(tx_ring, launch_time_offset, first_flag, 0, 0, 0);
> + meta_req->used_desc += 1;
> +}
> +
> const struct xsk_tx_metadata_ops igc_xsk_tx_metadata_ops = {
> .tmo_request_timestamp = igc_xsk_request_timestamp,
> .tmo_fill_timestamp = igc_xsk_fill_timestamp,
> + .tmo_request_launch_time = igc_xsk_request_launch_time,
> };
>
> static void igc_xdp_xmit_zc(struct igc_ring *ring)
> @@ -2998,7 +3033,13 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
> ntu = ring->next_to_use;
> budget = igc_desc_unused(ring);
>
> - while (xsk_tx_peek_desc(pool, &xdp_desc) && budget--) {
> + /* Packets with launch time require one data descriptor and one context
> + * descriptor. When the launch time falls into the next Qbv cycle, we
> + * may need to insert an empty packet, which requires two more
> + * descriptors. Therefore, to be safe, we always ensure we have at least
> + * 4 descriptors available.
> + */
> + while (xsk_tx_peek_desc(pool, &xdp_desc) && budget >= 4) {
> struct igc_metadata_request meta_req;
> struct xsk_tx_metadata *meta = NULL;
> struct igc_tx_buffer *bi;
> @@ -3019,9 +3060,19 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
> meta_req.tx_ring = ring;
> meta_req.tx_buffer = bi;
> meta_req.meta = meta;
> + meta_req.used_desc = 0;
> xsk_tx_metadata_request(meta, &igc_xsk_tx_metadata_ops,
> &meta_req);
>
> + /* xsk_tx_metadata_request() may have updated next_to_use */
> + ntu = ring->next_to_use;
> +
> + /* xsk_tx_metadata_request() may have updated Tx buffer info */
> + bi = meta_req.tx_buffer;
> +
> + /* xsk_tx_metadata_request() may use a few descriptors */
> + budget -= meta_req.used_desc;
> +
> tx_desc = IGC_TX_DESC(ring, ntu);
> tx_desc->read.cmd_type_len = cpu_to_le32(meta_req.cmd_type);
> tx_desc->read.olinfo_status = cpu_to_le32(olinfo_status);
> @@ -3039,9 +3090,11 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
> ntu++;
> if (ntu == ring->count)
> ntu = 0;
> +
> + ring->next_to_use = ntu;
> + budget--;
> }
>
> - ring->next_to_use = ntu;
> if (tx_desc) {
> igc_flush_tx_descriptors(ring);
> xsk_tx_release(pool);
> --
> 2.34.1
>
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