[PATCH] event/dsw: support explicit release only mode

[Mattias Rönnblom]

On 2024-05-27 17:35, Jerin Jacob wrote:
> On Sat, May 25, 2024 at 1:13 AM Mattias Rönnblom
> <mattias.ronnblom at ericsson.com> wrote:
>>
>> Add the RTE_EVENT_DEV_CAP_IMPLICIT_RELEASE_DISABLE capability to the
>> DSW event device.
>>
>> This feature may be used by an EAL thread to pull more work from the
>> work scheduler, without giving up the option to forward events
>> originating from a previous dequeue batch. This in turn allows an EAL
>> thread to be productive while waiting for a hardware accelerator to
>> complete some operation.
>>
>> Prior to this change, DSW didn't make any distinction between
>> RTE_EVENT_OP_FORWARD and RTE_EVENT_OP_NEW type events, other than that
>> new events would be backpressured earlier.
>>
>> After this change, DSW tracks the number of released events (i.e.,
>> events of type RTE_EVENT_OP_FORWARD and RTE_EVENT_OP_RELASE) that has
>> been enqueued.
>>
>> For efficency reasons, DSW does not track the *identity* of individual
>> events. This in turn implies that a certain stage in the flow
>> migration process, DSW must wait for all pending releases (on the
>> migration source port, only) to be received from the application, to
>> assure that no event pertaining to any of the to-be-migrated flows are
>> being processed.
>>
>> With this change, DSW starts making a distinction between forward and
>> new type events for credit allocation purposes. Only RTE_EVENT_OP_NEW
>> events needs credits. All events marked as RTE_EVENT_OP_FORWARD must
>> have a corresponding dequeued event from a previous dequeue batch.
>>
>> Flow migration for flows on RTE_SCHED_TYPE_PARALLEL queues remains
>> unaffected by this change.
>>
>> A side-effect of the tweaked DSW migration logic is that the migration
>> latency is reduced, regardless if implicit relase is enabled or not.
>>
>> Signed-off-by: Mattias Rönnblom <mattias.ronnblom at ericsson.com>
> 
> 
> 1) Update releases for PMD specific section for this new feature

Should the release note update be in the same patch, or a separate?

> 2) Fix CI issue as applicable
> 
> https://patches.dpdk.org/project/dpdk/patch/20240524192437.183960-1-mattias.ronnblom@ericsson.com/
> http://mails.dpdk.org/archives/test-report/2024-May/672848.html
> https://github.com/ovsrobot/dpdk/actions/runs/9229147658