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 at intel.com>
---
doc/guides/prog_guide/env_abstraction_layer.rst | 34 ++++++++++++++++++++++---
1 file changed, 31 insertions(+), 3 deletions(-)
diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst
b/doc/guides/prog_guide/env_abstraction_layer.rst
index cd4d666..f1b3ff1 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
~~~~~~~~~~~~
--
2.4.3
