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authorCunming Liang <cunming.liang@intel.com>2015-08-06 10:19:10 +0800
committerThomas Monjalon <thomas.monjalon@6wind.com>2015-08-10 23:31:45 +0200
commit5762a5657ee3a49daf5af2c64b6c4549d3ac8a80 (patch)
tree30ec0a0c02152a24351d15030bb0bebaf5c36242
parente9f64db946378944f149a0a198a01aa4f555748b (diff)
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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 <cunming.liang@intel.com> Acked-by: Danny Zhou <danny.zhou@intel.com>
-rw-r--r--doc/guides/prog_guide/env_abstraction_layer.rst34
1 files 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
~~~~~~~~~~~~