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Diffstat (limited to 'Documentation/networking/napi.rst')
| -rw-r--r-- | Documentation/networking/napi.rst | 50 |
1 files changed, 49 insertions, 1 deletions
diff --git a/Documentation/networking/napi.rst b/Documentation/networking/napi.rst index 7dd60366f4ff..4e008efebb35 100644 --- a/Documentation/networking/napi.rst +++ b/Documentation/networking/napi.rst @@ -263,7 +263,9 @@ are not well known). Busy polling is enabled by either setting ``SO_BUSY_POLL`` on selected sockets or using the global ``net.core.busy_poll`` and ``net.core.busy_read`` sysctls. An io_uring API for NAPI busy polling -also exists. +also exists. Threaded polling of NAPI also has a mode to busy poll for +packets (:ref:`threaded busy polling<threaded_busy_poll>`) using the NAPI +processing kthread. epoll-based busy polling ------------------------ @@ -426,6 +428,52 @@ Therefore, setting ``gro_flush_timeout`` and ``napi_defer_hard_irqs`` is the recommended usage, because otherwise setting ``irq-suspend-timeout`` might not have any discernible effect. +.. _threaded_busy_poll: + +Threaded NAPI busy polling +-------------------------- + +Threaded NAPI busy polling extends threaded NAPI and adds support to do +continuous busy polling of the NAPI. This can be useful for forwarding or +AF_XDP applications. + +Threaded NAPI busy polling can be enabled on per NIC queue basis using Netlink. + +For example, using the following script: + +.. code-block:: bash + + $ ynl --family netdev --do napi-set \ + --json='{"id": 66, "threaded": "busy-poll"}' + +The kernel will create a kthread that busy polls on this NAPI. + +The user may elect to set the CPU affinity of this kthread to an unused CPU +core to improve how often the NAPI is polled at the expense of wasted CPU +cycles. Note that this will keep the CPU core busy with 100% usage. + +Once threaded busy polling is enabled for a NAPI, PID of the kthread can be +retrieved using Netlink so the affinity of the kthread can be set up. + +For example, the following script can be used to fetch the PID: + +.. code-block:: bash + + $ ynl --family netdev --do napi-get --json='{"id": 66}' + +This will output something like following, the pid `258` is the PID of the +kthread that is polling this NAPI. + +.. code-block:: bash + + $ {'defer-hard-irqs': 0, + 'gro-flush-timeout': 0, + 'id': 66, + 'ifindex': 2, + 'irq-suspend-timeout': 0, + 'pid': 258, + 'threaded': 'busy-poll'} + .. _threaded: Threaded NAPI |