From 16eb4afc5d80c40a62d26cd459e89da74d602246 Mon Sep 17 00:00:00 2001 From: Michal Wilczynski Date: Tue, 15 Nov 2022 11:48:24 +0100 Subject: [PATCH] ice: Add documentation for devlink-rate implementation Add documentation to a newly added devlink-rate feature. Provide some examples on how to use the commands, which netlink attributes are supported and descriptions of the attributes. Signed-off-by: Michal Wilczynski Signed-off-by: Jakub Kicinski --- Documentation/networking/devlink/ice.rst | 115 +++++++++++++++++++++++ 1 file changed, 115 insertions(+) diff --git a/Documentation/networking/devlink/ice.rst b/Documentation/networking/devlink/ice.rst index 0c89ceb8986d..890062da7820 100644 --- a/Documentation/networking/devlink/ice.rst +++ b/Documentation/networking/devlink/ice.rst @@ -254,3 +254,118 @@ Users can request an immediate capture of a snapshot via the 0000000000000210 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 $ devlink region delete pci/0000:01:00.0/device-caps snapshot 1 + +Devlink Rate +============ + +The ``ice`` driver implements devlink-rate API. It allows for offload of +the Hierarchical QoS to the hardware. It enables user to group Virtual +Functions in a tree structure and assign supported parameters: tx_share, +tx_max, tx_priority and tx_weight to each node in a tree. So effectively +user gains an ability to control how much bandwidth is allocated for each +VF group. This is later enforced by the HW. + +It is assumed that this feature is mutually exclusive with DCB performed +in FW and ADQ, or any driver feature that would trigger changes in QoS, +for example creation of the new traffic class. The driver will prevent DCB +or ADQ configuration if user started making any changes to the nodes using +devlink-rate API. To configure those features a driver reload is necessary. +Correspondingly if ADQ or DCB will get configured the driver won't export +hierarchy at all, or will remove the untouched hierarchy if those +features are enabled after the hierarchy is exported, but before any +changes are made. + +This feature is also dependent on switchdev being enabled in the system. +It's required bacause devlink-rate requires devlink-port objects to be +present, and those objects are only created in switchdev mode. + +If the driver is set to the switchdev mode, it will export internal +hierarchy the moment VF's are created. Root of the tree is always +represented by the node_0. This node can't be deleted by the user. Leaf +nodes and nodes with children also can't be deleted. + +.. list-table:: Attributes supported + :widths: 15 85 + + * - Name + - Description + * - ``tx_max`` + - maximum bandwidth to be consumed by the tree Node. Rate Limit is + an absolute number specifying a maximum amount of bytes a Node may + consume during the course of one second. Rate limit guarantees + that a link will not oversaturate the receiver on the remote end + and also enforces an SLA between the subscriber and network + provider. + * - ``tx_share`` + - minimum bandwidth allocated to a tree node when it is not blocked. + It specifies an absolute BW. While tx_max defines the maximum + bandwidth the node may consume, the tx_share marks committed BW + for the Node. + * - ``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. + Range 0-7. Nodes with priority 7 have the highest priority and are + selected first, while nodes with priority 0 have the lowest + priority. Nodes that have the same priority are treated equally. + * - ``tx_weight`` + - allows for usage of Weighted Fair Queuing arbitration scheme among + siblings. This arbitration scheme can be used simultaneously with + the strict priority. Range 1-200. Only relative values mater for + arbitration. + +``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. + +.. code:: shell + + # enable switchdev + $ devlink dev eswitch set pci/0000:4b:00.0 mode switchdev + + # at this point driver should export internal hierarchy + $ echo 2 > /sys/class/net/ens785np0/device/sriov_numvfs + + $ devlink port function rate show + pci/0000:4b:00.0/node_25: type node parent node_24 + pci/0000:4b:00.0/node_24: type node parent node_0 + pci/0000:4b:00.0/node_32: type node parent node_31 + pci/0000:4b:00.0/node_31: type node parent node_30 + pci/0000:4b:00.0/node_30: type node parent node_16 + pci/0000:4b:00.0/node_19: type node parent node_18 + pci/0000:4b:00.0/node_18: type node parent node_17 + pci/0000:4b:00.0/node_17: type node parent node_16 + pci/0000:4b:00.0/node_14: type node parent node_5 + pci/0000:4b:00.0/node_5: type node parent node_3 + pci/0000:4b:00.0/node_13: type node parent node_4 + pci/0000:4b:00.0/node_12: type node parent node_4 + pci/0000:4b:00.0/node_11: type node parent node_4 + pci/0000:4b:00.0/node_10: type node parent node_4 + pci/0000:4b:00.0/node_9: type node parent node_4 + pci/0000:4b:00.0/node_8: type node parent node_4 + pci/0000:4b:00.0/node_7: type node parent node_4 + pci/0000:4b:00.0/node_6: type node parent node_4 + pci/0000:4b:00.0/node_4: type node parent node_3 + pci/0000:4b:00.0/node_3: type node parent node_16 + pci/0000:4b:00.0/node_16: type node parent node_15 + pci/0000:4b:00.0/node_15: type node parent node_0 + pci/0000:4b:00.0/node_2: type node parent node_1 + pci/0000:4b:00.0/node_1: type node parent node_0 + pci/0000:4b:00.0/node_0: type node + pci/0000:4b:00.0/1: type leaf parent node_25 + pci/0000:4b:00.0/2: type leaf parent node_25 + + # let's create some custom node + $ devlink port function rate add pci/0000:4b:00.0/node_custom parent node_0 + + # second custom node + $ devlink port function rate add pci/0000:4b:00.0/node_custom_1 parent node_custom + + # reassign second VF to newly created branch + $ devlink port function rate set pci/0000:4b:00.0/2 parent node_custom_1 + + # assign tx_weight to the VF + $ devlink port function rate set pci/0000:4b:00.0/2 tx_weight 5 + + # assign tx_share to the VF + $ devlink port function rate set pci/0000:4b:00.0/2 tx_share 500Mbps -- 2.39.5