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Documentation: Add documentation for new devlink-rate attributes

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Provide documentation for newly introduced netlink attributes for
devlink-rate: tx_priority and tx_weight.

Mention the possibility to export tree from the driver.

Signed-off-by: Michal Wilczynski <michal.wilczynski@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Michal Wilczynski 2022-11-15 11:48:25 +01:00 • committed by Jakub Kicinski
parent 16eb4afc5d
commit 242dd64375
1 changed files with 32 additions and 1 deletions
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Documentation/networking/devlink/devlink-port.rst
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@ -191,13 +191,44 @@ API allows to configure following rate object's parameters:
``tx_max`` ``tx_max``
Maximum TX rate value. Maximum TX rate value.
``tx_priority``
Allows for usage of strict priority arbiter among siblings. This
arbitration scheme attempts to schedule nodes based on their priority
as long as the nodes remain within their bandwidth limit. The higher the
priority the higher the probability that the node will get selected for
scheduling.
``tx_weight``
Allows for usage of Weighted Fair Queuing arbitration scheme among
siblings. This arbitration scheme can be used simultaneously with the
strict priority. As a node is configured with a higher rate it gets more
BW relative to it's siblings. Values are relative like a percentage
points, they basically tell how much BW should node take relative to
it's siblings.
``parent`` ``parent``
Parent node name. Parent node rate limits are considered as additional limits Parent node name. Parent node rate limits are considered as additional limits
to all node children limits. ``tx_max`` is an upper limit for children. to all node children limits. ``tx_max`` is an upper limit for children.
``tx_share`` is a total bandwidth distributed among children. ``tx_share`` is a total bandwidth distributed among children.
``tx_priority`` and ``tx_weight`` can be used simultaneously. In that case
nodes with the same priority form a WFQ subgroup in the sibling group
and arbitration among them is based on assigned weights.
Arbitration flow from the high level:
#. Choose a node, or group of nodes with the highest priority that stays
within the BW limit and are not blocked. Use ``tx_priority`` as a
parameter for this arbitration.
#. If group of nodes have the same priority perform WFQ arbitration on
that subgroup. Use ``tx_weight`` as a parameter for this arbitration.
#. Select the winner node, and continue arbitration flow among it's children,
until leaf node is reached, and the winner is established.
#. If all the nodes from the highest priority sub-group are satisfied, or
overused their assigned BW, move to the lower priority nodes.
Driver implementations are allowed to support both or either rate object types Driver implementations are allowed to support both or either rate object types
and setting methods of their parameters. and setting methods of their parameters. Additionally driver implementation
may export nodes/leafs and their child-parent relationships.
Terms and Definitions Terms and Definitions
===================== =====================