mirror of
https://github.com/torvalds/linux.git
synced 2024-11-28 07:01:32 +00:00
0db0c34cfb
This patch is born out of an investigation into which IEEE statistics correspond to which struct rtnl_link_stats64 members. Turns out that there seems to be reasonable consensus on the matter, among many drivers. To save others the time (and it took more time than I'm comfortable admitting) I'm adding comments referring to IEEE attributes to struct rtnl_link_stats64. Up until now we had two forms of documentation for stats - in Documentation/ABI/testing/sysfs-class-net-statistics and the comments on struct rtnl_link_stats64 itself. While the former is very cautious in defining the expected behavior, the latter feel quite dated and may not be easy to understand for modern day driver author (e.g. rx_over_errors). At the same time modern systems are far more complex and once obvious definitions lost their clarity. For example - does rx_packet count at the MAC layer (aFramesReceivedOK)? packets processed correctly by hardware? received by the driver? or maybe received by the stack? I tried to clarify the expectations, further clarifications from others are very welcome. The part hardest to untangle is rx_over_errors vs rx_fifo_errors vs rx_missed_errors. After much deliberation I concluded that for modern HW only two of the counters will make sense. The distinction between internal FIFO overflow and packets dropped due to back-pressure from the host is likely too implementation (driver and device) specific to expose in the standard stats. Now - which two of those counters we select to use is anyone's pick: sysfs documentation suggests rx_over_errors counts packets which did not fit into buffers due to MTU being too small, which I reused. There don't seem to be many modern drivers using it (well, CAN drivers seem to love this statistic). Of the remaining two I picked rx_missed_errors to report device drops. bnxt reports it and it's folded into "drop"s in procfs (while rx_fifo_errors is an error, and modern devices usually receive the frame OK, they just can't admit it into the pipeline). Of the drivers I looked at only AMD Lance-like and NS8390-like use all three of these counters. rx_missed_errors counts missed frames, rx_over_errors counts overflow events, and rx_fifo_errors counts frames which were truncated because they didn't fit into buffers. This suggests that rx_fifo_errors may be the correct stat for truncated packets, but I'd think a FIFO stat counting truncated packets would be very confusing to a modern reader. v2: - add driver developer notes about ethtool stat count and reset - replace Ethernet with IEEE 802.3 to better indicate source of attrs - mention byte counters don't count FCS - clarify RX counter is from device to host - drop "sightly" from sysfs paragraph - add examples of ethtool stats - s/incoming/received/ s/incoming/transmitted/ Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
||
|---|---|---|
| .. | ||
| asm-generic | ||
| drm | ||
| linux | ||
| misc | ||
| mtd | ||
| rdma | ||
| scsi | ||
| sound | ||
| video | ||
| xen | ||
| Kbuild | ||