diff options
Diffstat (limited to 'doc/guides/prog_guide/poll_mode_drv.rst')
| -rw-r--r-- | doc/guides/prog_guide/poll_mode_drv.rst | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/doc/guides/prog_guide/poll_mode_drv.rst b/doc/guides/prog_guide/poll_mode_drv.rst index 4987f70a..1ac8f7eb 100644 --- a/doc/guides/prog_guide/poll_mode_drv.rst +++ b/doc/guides/prog_guide/poll_mode_drv.rst @@ -84,7 +84,7 @@ Whenever needed and appropriate, asynchronous communication should be introduced Avoiding lock contention is a key issue in a multi-core environment. To address this issue, PMDs are designed to work with per-core private resources as much as possible. -For example, a PMD maintains a separate transmit queue per-core, per-port. +For example, a PMD maintains a separate transmit queue per-core, per-port, if the PMD is not ``DEV_TX_OFFLOAD_MT_LOCKFREE`` capable. In the same way, every receive queue of a port is assigned to and polled by a single logical core (lcore). To comply with Non-Uniform Memory Access (NUMA), memory management is designed to assign to each logical core @@ -146,6 +146,16 @@ This is also true for the pipe-line model provided all logical cores used are lo Multiple logical cores should never share receive or transmit queues for interfaces since this would require global locks and hinder performance. +If the PMD is ``DEV_TX_OFFLOAD_MT_LOCKFREE`` capable, multiple threads can invoke ``rte_eth_tx_burst()`` +concurrently on the same tx queue without SW lock. This PMD feature found in some NICs and useful in the following use cases: + +* Remove explicit spinlock in some applications where lcores are not mapped to Tx queues with 1:1 relation. + +* In the eventdev use case, avoid dedicating a separate TX core for transmitting and thus + enables more scaling as all workers can send the packets. + +See `Hardware Offload`_ for ``DEV_TX_OFFLOAD_MT_LOCKFREE`` capability probing details. + Device Identification and Configuration --------------------------------------- @@ -290,7 +300,8 @@ Hardware Offload Depending on driver capabilities advertised by ``rte_eth_dev_info_get()``, the PMD may support hardware offloading -feature like checksumming, TCP segmentation or VLAN insertion. +feature like checksumming, TCP segmentation, VLAN insertion or +lockfree multithreaded TX burst on the same TX queue. The support of these offload features implies the addition of dedicated status bit(s) and value field(s) into the rte_mbuf data structure, along |