This commit fixes a bug in which, when the sw PMD is reconfigured, it would
leave stale IQ chunk pointers in each queue's IQ structure. Now, the PMD
initializes all IQs at eventdev start time and releases all IQ chunk
pointers at eventdev stop time (which has the consequence that any events
in a queue when the eventdev is stopped will be lost). This approach should
be resilient to any reconfiguration done between the stop and start, such
as adding or removing queues.
This commit also fixes two potential issues in iq_chunk.h. iq_init()
now initializes the IQ's count field to 0, and iq_dequeue_burst() sets
iq->head to the appropriate next pointer.
Fixes: dca926ca9f ("event/sw: use dynamically-sized IQs")
Reported-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
Signed-off-by: Gage Eads <gage.eads@intel.com>
Reviewed-by: Harry van Haaren <harry.van.haaren@intel.com>
Acked-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
This commit introduces dynamically-sized IQs, by switching the underlying
data structure from a fixed-size ring to a linked list of queue 'chunks.'
This has a number of benefits:
- Certain corner cases were observed in which all of a pipeline's flows
could be pinned to one port for extended periods, effectively turning a
multi-core pipeline into single-core one. This was caused by an event
producer having a larger new_event_threshold than the IQ depth, and
injecting large numbers of packets that are ultimately backpressured in a
worker's rx_ring, causing those packets' flows to be scheduled to that
port.
The dynamically sized IQ does not have this problem because each IQ can
grow large enough to store all the system's events, such that
backpressure will not reach the worker_ring.
- Slight performance improvement (~1-2%) in high throughput scenarios,
tested with eventdev_pipeline_sw_pmd.
This implementation has a small increase in the queue storage memory
footprint (~70KB). This commit also removes the iq_size xstat, which no
longer applies to this implementation.
Signed-off-by: Gage Eads <gage.eads@intel.com>
Acked-by: Harry van Haaren <harry.van.haaren@intel.com>
