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Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/automake.mk | 1 | ||||
| -rw-r--r-- | Documentation/topics/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/topics/userspace-tx-steering.rst | 74 |
3 files changed, 76 insertions, 0 deletions
diff --git a/Documentation/automake.mk b/Documentation/automake.mk index 137cc57c5..01e3c4f9e 100644 --- a/Documentation/automake.mk +++ b/Documentation/automake.mk @@ -58,6 +58,7 @@ DOC_SOURCE = \ Documentation/topics/record-replay.rst \ Documentation/topics/tracing.rst \ Documentation/topics/userspace-tso.rst \ + Documentation/topics/userspace-tx-steering.rst \ Documentation/topics/windows.rst \ Documentation/howto/index.rst \ Documentation/howto/dpdk.rst \ diff --git a/Documentation/topics/index.rst b/Documentation/topics/index.rst index d8ccbd757..3699fd5c4 100644 --- a/Documentation/topics/index.rst +++ b/Documentation/topics/index.rst @@ -55,3 +55,4 @@ OVS userspace-tso idl-compound-indexes ovs-extensions + userspace-tx-steering diff --git a/Documentation/topics/userspace-tx-steering.rst b/Documentation/topics/userspace-tx-steering.rst new file mode 100644 index 000000000..16f066a8a --- /dev/null +++ b/Documentation/topics/userspace-tx-steering.rst @@ -0,0 +1,74 @@ +.. + Licensed under the Apache License, Version 2.0 (the "License"); you may + not use this file except in compliance with the License. You may obtain + a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + License for the specific language governing permissions and limitations + under the License. + + Convention for heading levels in Open vSwitch documentation: + + ======= Heading 0 (reserved for the title in a document) + ------- Heading 1 + ~~~~~~~ Heading 2 + +++++++ Heading 3 + ''''''' Heading 4 + + Avoid deeper levels because they do not render well. + +============================ +Userspace Tx packet steering +============================ + +The userspace datapath supports two transmit packet steering modes. + +Thread mode +~~~~~~~~~~~ + +This mode is automatically selected when the port's ``tx-steering`` option is +set to ``thread`` or unset. + +Depending on the port's number of Tx queues being greater or equal than the +number of PMD threads, static txq mapping or XPS will be used. + +This is the recommended mode for performance reasons if the number of Tx queues +is greater or equal to the number of PMD threads, because the Tx lock is not +acquired. + +If the number of Tx queues is greater than the number of threads, the remaining +Tx queues will not be used. + +This mode is enabled by default. + +Hash mode +~~~~~~~~~ + +Hash-based Tx packet steering mode distributes the packets on all the port's +transmit queues, whatever the number of PMD threads. The queue selection is +based on the 5-tuples hash to build the flows batches, the selected queue being +the modulo between the hash and the number of Tx queues of the port. + +Hash mode may be used for example with vhost-user ports, when the number of +vCPUs and queues of the guest are greater than the number of PMD threads. +Without hash mode, the Tx queues used would be limited to the number of +threads. + +Hash-based Tx packet steering may have an impact on the performance, given the +Tx lock acquisition is always required and a second level of batching is +performed. + +Usage +~~~~~ + +To enable hash mode:: + + $ ovs-vsctl set Interface <iface> other_config:tx-steering=hash + +To disable hash mode:: + + $ ovs-vsctl set Interface <iface> other_config:tx-steering=thread |