The 'Port/Rx Queue Assigment to PMD Threads' section has expanded over time and now includes info about stats/commands, manual pinning and different options for OVS assigning Rxqs to PMDs.
Split them into different sections with sub-headings and move the two similar paragraphs about stats together. Rename 'Automatic assignment of Port/Rx Queue to PMD Threads' section to 'PMD Automatic Load Balance'. A few other minor cleanups as I was reading. Signed-off-by: Kevin Traynor <[email protected]> Acked-by: Adrian Moreno <[email protected]> --- v3: - fixed minor comments from David's comments. v2: - a couple of small fixes as per Adrian's comments - remove duplicate PMD ALB conditions paragraph --- Documentation/topics/dpdk/pmd.rst | 103 +++++++++++++++--------------- 1 file changed, 53 insertions(+), 50 deletions(-) diff --git a/Documentation/topics/dpdk/pmd.rst b/Documentation/topics/dpdk/pmd.rst index 95fa7af12..e659fefef 100644 --- a/Documentation/topics/dpdk/pmd.rst +++ b/Documentation/topics/dpdk/pmd.rst @@ -75,8 +75,46 @@ for enabling things like multiqueue for :ref:`physical <dpdk-phy-multiqueue>` and :ref:`vhost-user <dpdk-vhost-user>` interfaces. -To show port/Rx queue assignment:: +Rx queues will be assigned to PMD threads by OVS, or they can be manually +pinned to PMD threads by the user. + +To see the port/Rx queue assignment and current measured usage history of PMD +core cycles for each Rx queue:: $ ovs-appctl dpif-netdev/pmd-rxq-show +.. note:: + + A history of one minute is recorded and shown for each Rx queue to allow for + traffic pattern spikes. Any changes in the Rx queue's PMD core cycles usage, + due to traffic pattern or reconfig changes, will take one minute to be fully + reflected in the stats. + + .. versionchanged:: 2.6.0 + + The ``pmd-rxq-show`` command was added in OVS 2.6.0. + +.. versionchanged:: 2.16.0 + + A ``overhead`` statistics is shown per PMD: it represents the number of + cycles inherently consumed by the OVS PMD processing loop. + +Rx queue to PMD assignment takes place whenever there are configuration changes +or can be triggered by using:: + + $ ovs-appctl dpif-netdev/pmd-rxq-rebalance + +.. versionchanged:: 2.9.0 + + Utilization-based allocation of Rx queues to PMDs and the + ``pmd-rxq-rebalance`` command were added in OVS 2.9.0. Prior to this, + allocation was round-robin and processing cycles were not taken into + consideration. + + In addition, the output of ``pmd-rxq-show`` was modified to include + Rx queue utilization of the PMD as a percentage. Prior to this, tracking of + stats was not available. + +Port/Rx Queue assignment to PMD threads by manual pinning +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Rx queues may be manually pinned to cores. This will change the default Rx queue assignment to PMD threads:: @@ -117,4 +155,6 @@ If using ``pmd-rxq-assign=group`` PMD threads with *pinned* Rxqs can be a *non-isolated* PMD, that will remain *non-isolated*. +Automatic Port/Rx Queue assignment to PMD threads +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If ``pmd-rxq-affinity`` is not set for Rx queues, they will be assigned to PMDs (cores) automatically. @@ -126,7 +166,9 @@ The algorithm used to automatically assign Rxqs to PMDs can be set by:: By default, ``cycles`` assignment is used where the Rxqs will be ordered by their measured processing cycles, and then be evenly assigned in descending -order to PMDs based on an up/down walk of the PMDs. For example, where there -are five Rx queues and three cores - 3, 7, and 8 - available and the measured -usage of core cycles per Rx queue over the last interval is seen to be: +order to PMDs. The PMD that will be selected for a given Rxq will be the next +one in alternating ascending/descending order based on core id. For example, +where there are five Rx queues and three cores - 3, 7, and 8 - available and +the measured usage of core cycles per Rx queue over the last interval is seen +to be: - Queue #0: 30% @@ -184,48 +226,11 @@ The Rx queues may be assigned to the cores in the following order:: Core 8: P1Q0 | -To see the current measured usage history of PMD core cycles for each Rx -queue:: - - $ ovs-appctl dpif-netdev/pmd-rxq-show - -.. note:: - - A history of one minute is recorded and shown for each Rx queue to allow for - traffic pattern spikes. Any changes in the Rx queue's PMD core cycles usage, - due to traffic pattern or reconfig changes, will take one minute to be fully - reflected in the stats. - -.. versionchanged:: 2.16.0 - - A ``overhead`` statistics is shown per PMD: it represents the number of - cycles inherently consumed by the OVS PMD processing loop. - -Rx queue to PMD assignment takes place whenever there are configuration changes -or can be triggered by using:: - - $ ovs-appctl dpif-netdev/pmd-rxq-rebalance - -.. versionchanged:: 2.6.0 - - The ``pmd-rxq-show`` command was added in OVS 2.6.0. - -.. versionchanged:: 2.9.0 - - Utilization-based allocation of Rx queues to PMDs and the - ``pmd-rxq-rebalance`` command were added in OVS 2.9.0. Prior to this, - allocation was round-robin and processing cycles were not taken into - consideration. - - In addition, the output of ``pmd-rxq-show`` was modified to include - Rx queue utilization of the PMD as a percentage. Prior to this, tracking of - stats was not available. - -Automatic assignment of Port/Rx Queue to PMD Threads (experimental) -------------------------------------------------------------------- +PMD Automatic Load Balance (experimental) +----------------------------------------- Cycle or utilization based allocation of Rx queues to PMDs gives efficient load distribution but it is not adaptive to change in traffic pattern -occurring over the time. This causes uneven load among the PMDs which results -in overall lower throughput. +occurring over the time. This may cause an uneven load among the PMDs which +results in overall lower throughput. To address this automatic load balancing of PMDs can be set by:: @@ -233,10 +238,8 @@ To address this automatic load balancing of PMDs can be set by:: $ ovs-vsctl set open_vswitch . other_config:pmd-auto-lb="true" -If pmd-auto-lb is set to true AND cycle based assignment is enabled then auto -load balancing of PMDs is enabled provided there are 2 or more non-isolated -PMDs and at least one of these PMDs is polling more than one RX queue. So, -following conditions need to be met to have Auto Load balancing enabled: +The following conditions need to be met to have Auto Load balancing +enabled: -1. cycle based assignment of RX queues to PMD is enabled. +1. cycle or group based assignment of RX queues to PMD is enabled. 2. pmd-auto-lb is set to true. 3. There are two or more non-isolated PMDs present. -- 2.31.1 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
