On Mon, Nov 9, 2026 at 8:00 AM Pravin Pathak <[email protected]> wrote: > > On Sat, Nov 7, 2026 at 2:29 AM Jerin Jacob <[email protected]> wrote: > > > > On Sat, Nov 7, 2026 at 7:00 AM Pravin Pathak <[email protected]> > > wrote: > > > > > > From: Pravin Pathak <[email protected]> > > > > > > This series introduces the Software Load Balancer (SLB) Eventdev PMD > > > (`event_slb`) supporting parallel, atomic and ordered queues. It is > > > a distributed software scheduler that scales well. > > > > > > Motivation > > > ---------- > > > Existing software eventdev PMDs face trade-offs between centralized > > > bottlenecks and feature coverage: > > > - `event_sw` relies on a dedicated centralized scheduler consuming > > > an extra CPU core. The single scheduling core also limits maximum > > > throughput and it does not scale. > > > - `event_dsw` distributes scheduling across worker cores without a > > > central scheduler core, but does not support ordered queues and > > > incurs per-port control ring messaging overhead during atomic flow > > > migrations. It also does not support service priority. > > > > > > Design Overview > > > --------------- > > > `event_slb` is a distributed (`RTE_EVENT_DEV_CAP_DISTRIBUTED_SCHED`), > > > maintenance-free (`RTE_EVENT_DEV_CAP_MAINTENANCE_FREE`) software eventdev > > > PMD that supports Atomic, Ordered, Parallel, and Single-Link queues: > > > > @[email protected] - drivers/event/dsw/ > > @[email protected] - drivers/event/opdl/ > > NO MAINTAINER for drivers/event/sw/ > > > > Hi Pravin, > > Creating new flavours. of evendev SW drivers is a maintenance burden, > > If this is close to DSW then please introduce mode in DSW driver and > > have function pointer switches for fastpath, > > Also claim should be backed by performance test values. Use > > testeventdev test cases and share the numbers to prove one way or > > another. > > > > In summary, IMO, it better to take NEW SW PMD when > > a)It operates completely different than DSW and SW and it is NOT > > possible to update existing SW PMDs > > b)Able to show better performance than existing drivers on the specific > > cases. > > > This driver is architecturally completely different from DSW. And it addresses > the gap of scalable software eventdev that can support ordered queues and > service priority. The skeleton is borrowed from DSW instead of writing > a new one. > But the underlying architecture is completely different. SLB uses > queues instead of > directly enquing to destination ports. DSW is an enqueue time scheduler > whereas SLB is a dequeue time scheduler. Very basic mechanism is different. > SLB does atomic flow migration is based on the port queue associated with the > atomic queue being full. It does not compute CPU load but checks if core is > able to serve the queue at mapped priority and if not, flows are migrated. > SLB is maintenance free unlike DSW. Flow migration happens without any > core-to-core communication required. SLB architecture allows extension to > support event priorities and configurable number of service priorities. > I will make patches with AI review fixes. AI comparison is matching > the structure and not underlying architecture. So it shows similarity.
Lets get the performance numbers for SLB vs DSW based on same test case so that we can decide. Performance and scalability will be the aspect to decide the usage of YET ANOTHER SW driver. > > > > > > > > 1. Queue-Centric Ring Architecture: > > > - Parallel and Single-Link queues map directly to `rte_event_ring` > > > instances (MP/MC for parallel, MP/SC for single-link), allowing > > > zero-copy burst enqueue and dequeue without history tracking. > > > - Ordered queues use the ring slot index at dequeue time as an implicit > > > sequence number into a per-queue reorder buffer, draining contiguous > > > completed events in order without global sequence counters. This > > > makes ordered queue implementaion highly efficient performing > > > close > > > to parallel queues. > > > - Atomic queues use a main MP/SC queue ring alongside per-port SP/SC > > > rings and a 2048-entry flow-to-port affinity table. All cores > > > served by the atomic queue are used for scheduling. > > > > > > 2. Lock-Free / Zero-Pause Atomic Flow Migration: > > > - When an atomic queue refills per-port rings and detects persistent > > > congestion on a destination port, SLB selects the lightest flow on > > > that port (outside the migration cooldown window) and waits for > > > queues in-flight events to drain naturally before switching the > > > flow's port affinity and schedule hold-buffer entries. > > > - Hold buffer is used for buffering events towards migrating ports > > > while allowing serving other ports. > > > - Implementaion avoids cross-port pause/unpause control rings while > > > preserving strict per-flow ordering. > > > > > > 3. Credit-Based Backpressure & Priority Scheduling: > > > - A global atomic credit pool with per-port local credit caches bounds > > > total in-flight events (`nb_events_limit`) and enforces > > > `new_event_threshold` with minimal atomic contention. > > > - Ports support two strict service priority levels with > > > round-robin scheduling within each priority level. > > > > > > 4. Observability & Testing: > > > - Device and per-port/per-queue extended statistics (`xstats`), > > > detailed `rte_event_dev_dump()` diagnostics, and a unit self-test > > > suite (`eventdev_selftest_slb`) covering parallel, atomic, ordered, > > > single-link, priority, backpressure, stop-flush, and multi-core > > > atomic migration scenarios. > > > > > > 5. Future Plan: > > > - Supporting Event priority > > > - Optimizing atomic flow migration > > > > > > Pravin Pathak (8): > > > event/slb: introduce software load balancer PMD > > > event/slb: add support for ordered queues > > > event/slb: add support for atomic queues > > > event/slb: add dynamic flow migration for atomic queues > > > event/slb: add extended statistics and diagnostics > > > event/slb: add self-test and documentation > > > event/slb: update resets and credit defaults > > > event/slb: improve port linking, config checks and atomic refill > > > > > > MAINTAINERS | 6 + > > > app/test/test_eventdev.c | 7 + > > > doc/guides/eventdevs/features/slb.ini | 25 + > > > doc/guides/eventdevs/index.rst | 1 + > > > doc/guides/eventdevs/slb.rst | 61 ++ > > > drivers/event/meson.build | 1 + > > > drivers/event/slb/meson.build | 21 + > > > drivers/event/slb/slb_evdev.c | 904 ++++++++++++++++++ > > > drivers/event/slb/slb_evdev.h | 263 ++++++ > > > drivers/event/slb/slb_event.c | 1219 +++++++++++++++++++++++++ > > > drivers/event/slb/slb_selftest.c | 522 +++++++++++ > > > drivers/event/slb/slb_xstats.c | 347 +++++++ > > > 12 files changed, 3377 insertions(+) > > > create mode 100644 doc/guides/eventdevs/features/slb.ini > > > create mode 100644 doc/guides/eventdevs/slb.rst > > > create mode 100644 drivers/event/slb/meson.build > > > create mode 100644 drivers/event/slb/slb_evdev.c > > > create mode 100644 drivers/event/slb/slb_evdev.h > > > create mode 100644 drivers/event/slb/slb_event.c > > > create mode 100644 drivers/event/slb/slb_selftest.c > > > create mode 100644 drivers/event/slb/slb_xstats.c > > > > > > -- > > > 2.53.0 > > >
