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d7c3a7ff75
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@intel.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://patch.msgid.link/20250216093430.957880-6-yoong.siang.song@intel.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.