Devlink Resource

devlink provides the ability for drivers to register resources, which can allow administrators to see the device restrictions for a given resource, as well as how much of the given resource is currently in use. Additionally, these resources can optionally have configurable size. This could enable the administrator to limit the number of resources that are used.

For example, the netdevsim driver enables /IPv4/fib and /IPv4/fib-rules as resources to limit the number of IPv4 FIB entries and rules for a given device.

Resource Ids

Each resource is represented by an id, and contains information about its current size and related sub resources. To access a sub resource, you specify the path of the resource. For example /IPv4/fib is the id for the fib sub-resource under the IPv4 resource.

Generic Resources

Generic resources are used to describe resources that can be shared by multiple device drivers and their description must be added to the following table:

List of Generic Resources

Name	Description
physical_ports	A limited capacity of physical ports that the switch ASIC can support

example usage

The resources exposed by the driver can be observed, for example:

$devlink resource show pci/0000:03:00.0
pci/0000:03:00.0:
  name kvd size 245760 unit entry
    resources:
      name linear size 98304 occ 0 unit entry size_min 0 size_max 147456 size_gran 128
      name hash_double size 60416 unit entry size_min 32768 size_max 180224 size_gran 128
      name hash_single size 87040 unit entry size_min 65536 size_max 212992 size_gran 128

Some resource’s size can be changed. Examples:

$devlink resource set pci/0000:03:00.0 path /kvd/hash_single size 73088
$devlink resource set pci/0000:03:00.0 path /kvd/hash_double size 74368

The changes do not apply immediately, this can be validated by the ‘size_new’ attribute, which represents the pending change in size. For example:

$devlink resource show pci/0000:03:00.0
pci/0000:03:00.0:
  name kvd size 245760 unit entry size_valid false
  resources:
    name linear size 98304 size_new 147456 occ 0 unit entry size_min 0 size_max 147456 size_gran 128
    name hash_double size 60416 unit entry size_min 32768 size_max 180224 size_gran 128
    name hash_single size 87040 unit entry size_min 65536 size_max 212992 size_gran 128

Note that changes in resource size may require a device reload to properly take effect.

Port-level Resources and Full Dump

In addition to device-level resources, devlink also supports port-level resources. These resources are associated with a specific devlink port rather than the device as a whole.

To list resources for all devlink devices and ports:

$ devlink resource show
pci/0000:03:00.0:
  name max_local_SFs size 128 unit entry dpipe_tables none
  name max_external_SFs size 128 unit entry dpipe_tables none
pci/0000:03:00.0/196608:
  name max_SFs size 128 unit entry dpipe_tables none
pci/0000:03:00.0/196609:
  name max_SFs size 128 unit entry dpipe_tables none
pci/0000:03:00.1:
  name max_local_SFs size 128 unit entry dpipe_tables none
  name max_external_SFs size 128 unit entry dpipe_tables none
pci/0000:03:00.1/196708:
  name max_SFs size 128 unit entry dpipe_tables none
pci/0000:03:00.1/196709:
  name max_SFs size 128 unit entry dpipe_tables none

To show resources for a specific port:

$ devlink resource show pci/0000:03:00.0/196608
pci/0000:03:00.0/196608:
  name max_SFs size 128 unit entry dpipe_tables none

Resource Scope Filtering

When dumping resources for all devices, devlink resource show accepts an optional scope parameter to restrict the response to device-level resources, port-level resources, or both (the default).

To dump only device-level resources across all devices:

$ devlink resource show scope dev
pci/0000:03:00.0:
  name max_local_SFs size 128 unit entry dpipe_tables none
  name max_external_SFs size 128 unit entry dpipe_tables none
pci/0000:03:00.1:
  name max_local_SFs size 128 unit entry dpipe_tables none
  name max_external_SFs size 128 unit entry dpipe_tables none

To dump only port-level resources across all devices:

$ devlink resource show scope port
pci/0000:03:00.0/196608:
  name max_SFs size 128 unit entry dpipe_tables none
pci/0000:03:00.0/196609:
  name max_SFs size 128 unit entry dpipe_tables none
pci/0000:03:00.1/196708:
  name max_SFs size 128 unit entry dpipe_tables none
pci/0000:03:00.1/196709:
  name max_SFs size 128 unit entry dpipe_tables none

Note that port-level resources are read-only.