Add a couple of hints on how to retrieve and implement generic XDP statistics for drivers/interfaces. Mention that it's unwanted to include related XDP counters in driver-defined Ethtool stats. Signed-off-by: Alexander Lobakin <alexandr.lobakin@xxxxxxxxx> --- Documentation/networking/statistics.rst | 33 +++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/Documentation/networking/statistics.rst b/Documentation/networking/statistics.rst index c9aeb70dafa2..ec5d14f279e1 100644 --- a/Documentation/networking/statistics.rst +++ b/Documentation/networking/statistics.rst @@ -41,6 +41,29 @@ If `-s` is specified once the detailed errors won't be shown. `ip` supports JSON formatting via the `-j` option. +For some interfaces, standard XDP statistics are available. +It can be accessed the same ways, e.g. `ip`:: + + $ ip link xdpstats dev enp178s0 + 16: enp178s0: + xdp-channel0-rx_xdp_packets: 0 + xdp-channel0-rx_xdp_bytes: 1 + xdp-channel0-rx_xdp_errors: 2 + xdp-channel0-rx_xdp_aborted: 3 + xdp-channel0-rx_xdp_drop: 4 + xdp-channel0-rx_xdp_invalid: 5 + xdp-channel0-rx_xdp_pass: 6 + xdp-channel0-rx_xdp_redirect: 7 + xdp-channel0-rx_xdp_redirect_errors: 8 + xdp-channel0-rx_xdp_tx: 9 + xdp-channel0-rx_xdp_tx_errors: 10 + xdp-channel0-tx_xdp_xmit_packets: 11 + xdp-channel0-tx_xdp_xmit_bytes: 12 + xdp-channel0-tx_xdp_xmit_errors: 13 + xdp-channel0-tx_xdp_xmit_full: 14 + +Those are usually per-channel. JSON is also supported via the `-j` opt. + Protocol-specific statistics ---------------------------- @@ -147,6 +170,8 @@ Statistics are reported both in the responses to link information requests (`RTM_GETLINK`) and statistic requests (`RTM_GETSTATS`, when `IFLA_STATS_LINK_64` bit is set in the `.filter_mask` of the request). +`IFLA_STATS_LINK_XDP_XSTATS` bit is used to retrieve standard XDP statstics. + ethtool ------- @@ -206,6 +231,14 @@ Retrieving ethtool statistics is a multi-syscall process, drivers are advised to keep the number of statistics constant to avoid race conditions with user space trying to read them. +It is up to the developers whether to implement XDP statistics or not due to +possible performance hits. If so, it is encouraged to export it using generic +XDP statistics infrastructure, not driver-defined Ethtool stats. +It can be achieve by implementing `.ndo_get_xdp_stats` and, optionally but +preferred, `.ndo_get_xdp_stats_nch`. There are several common helper structures +and functions in `include/net/xdp.h` to make this simpler and keep the code +compact. + Statistics must persist across routine operations like bringing the interface down and up. -- 2.33.1
