[PATCH bpf-next v6 4/4] igc: Add launch time support to XDP ZC
Abdul Rahim, Faizal
faizal.abdul.rahim at linux.intel.com
Sun Jan 19 22:25:45 PST 2025
Hi Siang.
On 16/1/2025 11:53 pm, Song Yoong Siang wrote:
> Enable Launch Time Control (LTC) support to XDP zero copy via XDP Tx
> metadata framework.
>
> This patch is tested with tools/testing/selftests/bpf/xdp_hw_metadata on
> Intel I225-LM Ethernet controller. Below are the test steps and result.
>
> Test Steps:
> 1. At DUT, start xdp_hw_metadata selftest application:
> $ sudo ./xdp_hw_metadata enp2s0 -l 1000000000 -L 1
>
> 2. At Link Partner, send an UDP packet with VLAN priority 1 to port 9091 of
> DUT.
>
> When launch time is set to 1s in the future, the delta between launch time
> and transmit hardware timestamp is equal to 0.016us, as shown in result
> 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
To be cautious, could we perform a stress test by sending a higher number
of packets with launch time? For example, we could send 200 packets, each
configured with a launch time, and verify that the driver continues to
function correctly afterward.
> Signed-off-by: Song Yoong Siang <yoong.siang.song at intel.com>
> ---
> drivers/net/ethernet/intel/igc/igc_main.c | 78 ++++++++++++++++-------
> 1 file changed, 56 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 27872bdea9bd..6857f5f5b4b2 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -1566,6 +1566,26 @@ static bool igc_request_tx_tstamp(struct igc_adapter *adapter, struct sk_buff *s
> return false;
> }
>
> +static void igc_insert_empty_packet(struct igc_ring *tx_ring)
> +{
> + struct igc_tx_buffer *empty_info;
> + struct sk_buff *empty;
> + void *data;
> +
> + empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
> + empty = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC);
> + if (!empty)
> + return;
> +
> + data = skb_put(empty, IGC_EMPTY_FRAME_SIZE);
> + memset(data, 0, IGC_EMPTY_FRAME_SIZE);
> +
> + igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0);
> +
> + if (igc_init_tx_empty_descriptor(tx_ring, empty, empty_info) < 0)
> + dev_kfree_skb_any(empty);
> +}
> +
The function igc_insert_empty_packet() appears to wrap existing code to
enhance reusability, with no new changes related to enabling launch-time
XDP ZC functionality. If so, could we split this into a separate commit?
This would make it clearer for the reader to distinguish between the
refactoring changes and the new changes related to enabling launch-time XDP
ZC support.
> static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb,
> struct igc_ring *tx_ring)
> {
> @@ -1603,26 +1623,8 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb,
> skb->tstamp = ktime_set(0, 0);
> launch_time = igc_tx_launchtime(tx_ring, txtime, &first_flag, &insert_empty);
>
> - if (insert_empty) {
> - struct igc_tx_buffer *empty_info;
> - struct sk_buff *empty;
> - void *data;
> -
> - empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
> - empty = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC);
> - if (!empty)
> - goto done;
> -
> - data = skb_put(empty, IGC_EMPTY_FRAME_SIZE);
> - memset(data, 0, IGC_EMPTY_FRAME_SIZE);
> -
> - igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0);
> -
> - if (igc_init_tx_empty_descriptor(tx_ring,
> - empty,
> - empty_info) < 0)
> - dev_kfree_skb_any(empty);
> - }
> + if (insert_empty)
> + igc_insert_empty_packet(tx_ring);
>
> done:
> /* record the location of the first descriptor for this packet */
> @@ -2955,9 +2957,33 @@ 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) {
> + igc_insert_empty_packet(tx_ring);
> + meta_req->tx_buffer =
> + &tx_ring->tx_buffer_info[tx_ring->next_to_use];
> + }
> +
> + igc_tx_ctxtdesc(tx_ring, launch_time_offset, first_flag, 0, 0, 0);
> +}
> +
> 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)
> @@ -2980,7 +3006,7 @@ 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--) {
> + while (xsk_tx_peek_desc(pool, &xdp_desc) && budget >= 4) {
Could we add some explanation on what & why the value "4" is used ?
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