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a61a459f58
Testing a network device that has large numbers of bytes/packets may
overflow. Using stats64 when comparing fixes this problem.
I tripped on this while iterating on a qstats patch for mlx5. See below
for confirmation without my added code that this is a bug.
Before this patch (with added debugging output):
$ NETIF=eth0 tools/testing/selftests/drivers/net/stats.py
KTAP version 1
1..4
ok 1 stats.check_pause
ok 2 stats.check_fec
rstat: 481708634 qstat: 666201639514 key: tx-bytes
not ok 3 stats.pkt_byte_sum
ok 4 stats.qstat_by_ifindex
Note the huge delta above ^^^ in the rtnl vs qstats.
After this patch:
$ NETIF=eth0 tools/testing/selftests/drivers/net/stats.py
KTAP version 1
1..4
ok 1 stats.check_pause
ok 2 stats.check_fec
ok 3 stats.pkt_byte_sum
ok 4 stats.qstat_by_ifindex
It looks like rtnl_fill_stats in net/core/rtnetlink.c will attempt to
copy the 64bit stats into a 32bit structure which is probably why this
behavior is occurring.
To show this is happening, you can get the underlying stats that the
stats.py test uses like this:
$ ./cli.py --spec ../../../Documentation/netlink/specs/rt_link.yaml \
--do getlink --json '{"ifi-index": 7}'
And examine the output (heavily snipped to show relevant fields):
'stats': {
'multicast': 3739197,
'rx-bytes': 1201525399,
'rx-packets': 56807158,
'tx-bytes': 492404458,
'tx-packets': 1200285371,
'stats64': {
'multicast': 3739197,
'rx-bytes': 35561263767,
'rx-packets': 56807158,
'tx-bytes': 666212335338,
'tx-packets': 1200285371,
The stats.py test prior to this patch was using the 'stats' structure
above, which matches the failure output on my system.
Comparing side by side, rx-bytes and tx-bytes, and getting ethtool -S
output:
rx-bytes stats: 1201525399
rx-bytes stats64: 35561263767
rx-bytes ethtool: 36203402638
tx-bytes stats: 492404458
tx-bytes stats64: 666212335338
tx-bytes ethtool: 666215360113
Note that the above was taken from a system with an mlx5 NIC, which only
exposes ndo_get_stats64.
Based on the ethtool output and qstat output, it appears that stats.py
should be updated to use the 'stats64' structure for accurate
comparisons when packet/byte counters get very large.
To confirm that this was not related to the qstats code I was iterating
on, I booted a kernel without my driver changes and re-ran the test
which shows the qstats are skipped (as they don't exist for mlx5):
NETIF=eth0 tools/testing/selftests/drivers/net/stats.py
KTAP version 1
1..4
ok 1 stats.check_pause
ok 2 stats.check_fec
ok 3 stats.pkt_byte_sum # SKIP qstats not supported by the device
ok 4 stats.qstat_by_ifindex # SKIP No ifindex supports qstats
But, fetching the stats using the CLI
$ ./cli.py --spec ../../../Documentation/netlink/specs/rt_link.yaml \
--do getlink --json '{"ifi-index": 7}'
Shows the same issue (heavily snipped for relevant fields only):
'stats': {
'multicast': 105489,
'rx-bytes': 530879526,
'rx-packets': 751415,
'tx-bytes': 2510191396,
'tx-packets': 27700323,
'stats64': {
'multicast': 105489,
'rx-bytes': 530879526,
'rx-packets': 751415,
'tx-bytes': 15395093284,
'tx-packets': 27700323,
Comparing side by side with ethtool -S on the unmodified mlx5 driver:
tx-bytes stats: 2510191396
tx-bytes stats64: 15395093284
tx-bytes ethtool: 17718435810
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.