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| author | Jakub Kicinski <kuba@kernel.org> | 2023-04-20 16:33:02 -0700 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2023-04-24 18:09:49 -0700 |
| commit | 00d0f31a1ec8eb3e4d692bdf2455daf0fb865bb3 (patch) | |
| tree | c84b007b7541fee91aa42b66b6beb51fbf1e6804 /Documentation/networking | |
| parent | 086c161678b8cc291aa21ff8ef2b53df83ee44aa (diff) | |
| download | lwn-00d0f31a1ec8eb3e4d692bdf2455daf0fb865bb3.tar.gz lwn-00d0f31a1ec8eb3e4d692bdf2455daf0fb865bb3.zip | |
net: ethtool: coalesce: try to make user settings stick twice
SET_COALESCE may change operation mode and parameters in one call.
Changing operation mode may cause the driver to reset the parameter
values to what is a reasonable default for new operation mode.
Since driver does not know which parameters come from user and which
are echoed back from ->get, driver may ignore the parameters when
switching operation modes.
This used to be inevitable for ioctl() but in netlink we know which
parameters are actually specified by the user.
We could inform which parameters were set by the user but this would
lead to a lot of code duplication in the drivers. Instead try to call
the drivers twice if both mode and params are changed. The set method
already checks if any params need updating so in case the driver did
the right thing the first time around - there will be no second call
to it's ->set method (only an extra call to ->get()).
For mlx5 for example before this patch we'd see:
# ethtool -C eth0 adaptive-rx on adaptive-tx on
# ethtool -C eth0 adaptive-rx off adaptive-tx off \
tx-usecs 123 rx-usecs 123
Adaptive RX: off TX: off
rx-usecs: 3
rx-frames: 32
tx-usecs: 16
tx-frames: 32
[...]
After the change:
# ethtool -C eth0 adaptive-rx on adaptive-tx on
# ethtool -C eth0 adaptive-rx off adaptive-tx off \
tx-usecs 123 rx-usecs 123
Adaptive RX: off TX: off
rx-usecs: 123
rx-frames: 32
tx-usecs: 123
tx-frames: 32
[...]
This only works for netlink, so it's a small discrepancy between
netlink and ioctl(). Since we anticipate most users to move to
netlink I believe it's worth making their lives easier.
Link: https://lore.kernel.org/r/20230420233302.944382-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'Documentation/networking')
| -rw-r--r-- | Documentation/networking/ethtool-netlink.rst | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst index cd0973d4ba01..2540c70952ff 100644 --- a/Documentation/networking/ethtool-netlink.rst +++ b/Documentation/networking/ethtool-netlink.rst @@ -1099,6 +1099,10 @@ such that the corresponding bit in ``ethtool_ops::supported_coalesce_params`` is not set), regardless of their values. Driver may impose additional constraints on coalescing parameters and their values. +Compared to requests issued via the ``ioctl()`` netlink version of this request +will try harder to make sure that values specified by the user have been applied +and may call the driver twice. + PAUSE_GET ========= |