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doc: add Rx interrupt in prog guide

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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 <cunming.liang@intel.com>
Acked-by: Danny Zhou <danny.zhou@intel.com>
This commit is contained in:
Cunming Liang 2015-08-06 10:19:10 +08:00 committed by Thomas Monjalon
parent e9f64db946
commit 5762a5657e
1 changed files with 31 additions and 3 deletions
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34
doc/guides/prog_guide/env_abstraction_layer.rst
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@ -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
~~~~~~~~~~~~