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

[Jerin Jacob <jerinjacobk@gmail.com>]

On Sat, May 25, 2024 at 1:13 AM Mattias Rönnblom
<mattias.ronnblom@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@ericsson.com>


1) Update releases for PMD specific section for this new feature
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