From: Cunming Liang Date: Thu, 6 Aug 2015 02:19:10 +0000 (+0800) Subject: doc: add Rx interrupt in prog guide X-Git-Tag: spdx-start~8543 X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=5762a5657ee3a49daf5af2c64b6c4549d3ac8a80;p=dpdk.git doc: add Rx interrupt in prog guide The patch updates the env_abstraction_layer.rst part in prog_guide. It adds the RX interrupt event declaration and revises the others in interrupt event section. Signed-off-by: Cunming Liang Acked-by: Danny Zhou --- diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst index cd4d66686f..f1b3ff1be9 100644 --- a/doc/guides/prog_guide/env_abstraction_layer.rst +++ b/doc/guides/prog_guide/env_abstraction_layer.rst @@ -166,8 +166,10 @@ CPU Feature Identification The EAL can query the CPU at runtime (using the rte_cpu_get_feature() function) to determine which CPU features are available. -User Space Interrupt and Alarm Handling -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +User Space Interrupt Event +~~~~~~~~~~~~~~~~~~~~~~~~~~ + ++ User Space Interrupt and Alarm Handling in Host Thread The EAL creates a host thread to poll the UIO device file descriptors to detect the interrupts. Callbacks can be registered or unregistered by the EAL functions for a specific interrupt event @@ -176,9 +178,35 @@ The EAL also allows timed callbacks to be used in the same way as for NIC interr .. note:: - The only interrupts supported by the DPDK Poll-Mode Drivers are those for link status change, + In DPDK PMD, the only interrupts handled by the dedicated host thread are those for link status change, i.e. link up and link down notification. + ++ RX Interrupt Event + +The receive and transmit routines provided by each PMD don't limit themselves to execute in polling thread mode. +To ease the idle polling with tiny throughput, it's useful to pause the polling and wait until the wake-up event happens. +The RX interrupt is the first choice to be such kind of wake-up event, but probably won't be the only one. + +EAL provides the event APIs for this event-driven thread mode. +Taking linuxapp as an example, the implementation relies on epoll. Each thread can monitor an epoll instance +in which all the wake-up events' file descriptors are added. The event file descriptors are created and mapped to +the interrupt vectors according to the UIO/VFIO spec. +From bsdapp's perspective, kqueue is the alternative way, but not implemented yet. + +EAL initializes the mapping between event file descriptors and interrupt vectors, while each device initializes the mapping +between interrupt vectors and queues. In this way, EAL actually is unaware of the interrupt cause on the specific vector. +The eth_dev driver takes responsibility to program the latter mapping. + +.. note:: + + Per queue RX interrupt event is only allowed in VFIO which supports multiple MSI-X vector. In UIO, the RX interrupt + together with other interrupt causes shares the same vector. In this case, when RX interrupt and LSC(link status change) + interrupt are both enabled(intr_conf.lsc == 1 && intr_conf.rxq == 1), only the former is capable. + +The RX interrupt are controlled/enabled/disabled by ethdev APIs - 'rte_eth_dev_rx_intr_*'. They return failure if the PMD +hasn't support them yet. The intr_conf.rxq flag is used to turn on the capability of RX interrupt per device. + Blacklisting ~~~~~~~~~~~~