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76abb5d675
Add support for reading the statistics counters, if they are enabled. The counters may be 64-bit, but we can't detect this statically as there's no ability bit for it and the counters are read-only. Therefore, we assume the counters are 32-bits by default. To ensure we don't miss an overflow, we read all counters at 13-second intervals. This should be often enough to ensure the bytes counters don't wrap at 2.5 Gbit/s. Another complication is that the counters may be reset when the device is reset (depending on configuration). To ensure the counters persist across link up/down (including suspend/resume), we maintain our own versions along with the last counter value we saw. Because we might wait up to 100 ms for the reset to complete, we use a mutex to protect writing hw_stats. We can't sleep in ndo_get_stats64, so we use a seqlock to protect readers. We don't bother disabling the refresh work when we detect 64-bit counters. This is because the reset issue requires us to read hw_stat_base and reset_in_progress anyway, which would still require the seqcount. And I don't think skipping the task is worth the extra bookkeeping. We can't use the byte counters for either get_stats64 or get_eth_mac_stats. This is because the byte counters include everything in the frame (destination address to FCS, inclusive). But rtnl_link_stats64 wants bytes excluding the FCS, and ethtool_eth_mac_stats wants to exclude the L2 overhead (addresses and length/type). It might be possible to calculate the byte values Linux expects based on the frame counters, but I think it is simpler to use the existing software counters. get_ethtool_stats is implemented for nonstandard statistics. This includes the aforementioned byte counters, VLAN and PFC frame counters, and user-defined (e.g. with custom RTL) counters. Signed-off-by: Sean Anderson <sean.anderson@linux.dev> Link: https://patch.msgid.link/20240820175343.760389-3-sean.anderson@linux.dev Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
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.