[PATCH v5 1/3] lib: introduce dispatcher library

["Mattias Rönnblom" <mattias.ronnblom@ericsson.com>]

The purpose of the dispatcher library is to help reduce coupling in an
Eventdev-based DPDK application.

In addition, the dispatcher also provides a convenient and flexible
way for the application to use service cores for application-level
processing.

Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
Tested-by: Peter Nilsson <peter.j.nilsson@ericsson.com>
Reviewed-by: Heng Wang <heng.wang@ericsson.com>

--

PATCH v5:
 o Move from using an integer id to a pointer to reference a dispatcher
   instance, to simplify the API.
 o Fix bug where dispatcher stats retrieval function erroneously depended
   on the user-supplied stats buffer being all-zero.

PATCH v4:
 o Fix bugs in handler and finalizer unregistration. (Naga Harish)
 o Return -EINVAL in cases where NULL pointers were provided in
   calls requiring non-NULL pointers. (Naga Harish)
 o Add experimental warning for the whole API. (Jerin Jacob)

PATCH v3:
 o To underline its optional character and since it does not provide
   hardware abstraction, the event dispatcher is now a separate
   library.
 o Change name from rte_event_dispatcher -> rte_dispatcher, to make it
   shorter and to avoid the rte_event_* namespace.

PATCH v2:
 o Add dequeue batch count statistic.
 o Add statistics reset function to API.
 o Clarify MT safety guarantees (or lack thereof) in the API documentation.
 o Change loop variable type in evd_lcore_get_handler_by_id() to uint16_t,
   to be consistent with similar loops elsewhere in the dispatcher.
 o Fix variable names in finalizer unregister function.

PATCH:
 o Change prefix from RED to EVD, to avoid confusion with random
   early detection.

RFC v4:
 o Move handlers to per-lcore data structures.
 o Introduce mechanism which rearranges handlers so that often-used
   handlers tend to be tried first.
 o Terminate dispatch loop in case all events are delivered.
 o To avoid the dispatcher's service function hogging the CPU, process
   only one batch per call.
 o Have service function return -EAGAIN if no work is performed.
 o Events delivered in the process function is no longer marked 'const',
   since modifying them may be useful for the application and cause
   no difficulties for the dispatcher.
 o Various minor API documentation improvements.

RFC v3:
 o Add stats_get() function to the version.map file.
---
 MAINTAINERS                     |   3 +
 doc/api/doxy-api-index.md       |   1 +
 doc/api/doxy-api.conf.in        |   1 +
 lib/dispatcher/meson.build      |  17 +
 lib/dispatcher/rte_dispatcher.c | 708 ++++++++++++++++++++++++++++++++
 lib/dispatcher/rte_dispatcher.h | 468 +++++++++++++++++++++
 lib/dispatcher/version.map      |  20 +
 lib/meson.build                 |   2 +
 8 files changed, 1220 insertions(+)
 create mode 100644 lib/dispatcher/meson.build
 create mode 100644 lib/dispatcher/rte_dispatcher.c
 create mode 100644 lib/dispatcher/rte_dispatcher.h
 create mode 100644 lib/dispatcher/version.map

diff --git a/MAINTAINERS b/MAINTAINERS
index a926155f26..6704cd5b2c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1726,6 +1726,9 @@ M: Nithin Dabilpuram <ndabilpuram@marvell.com>
 M: Pavan Nikhilesh <pbhagavatula@marvell.com>
 F: lib/node/
 
+Dispatcher - EXPERIMENTAL
+M: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
+F: lib/dispatcher/
 
 Test Applications
 -----------------
diff --git a/doc/api/doxy-api-index.md b/doc/api/doxy-api-index.md
index fdeda13932..7d0cad9fed 100644
--- a/doc/api/doxy-api-index.md
+++ b/doc/api/doxy-api-index.md
@@ -155,6 +155,7 @@ The public API headers are grouped by topics:
 
 - **classification**
   [reorder](@ref rte_reorder.h),
+  [dispatcher](@ref rte_dispatcher.h),
   [distributor](@ref rte_distributor.h),
   [EFD](@ref rte_efd.h),
   [ACL](@ref rte_acl.h),
diff --git a/doc/api/doxy-api.conf.in b/doc/api/doxy-api.conf.in
index a88accd907..59c679e621 100644
--- a/doc/api/doxy-api.conf.in
+++ b/doc/api/doxy-api.conf.in
@@ -34,6 +34,7 @@ INPUT                   = @TOPDIR@/doc/api/doxy-api-index.md \
                           @TOPDIR@/lib/cmdline \
                           @TOPDIR@/lib/compressdev \
                           @TOPDIR@/lib/cryptodev \
+                          @TOPDIR@/lib/dispatcher \
                           @TOPDIR@/lib/distributor \
                           @TOPDIR@/lib/dmadev \
                           @TOPDIR@/lib/efd \
diff --git a/lib/dispatcher/meson.build b/lib/dispatcher/meson.build
new file mode 100644
index 0000000000..c6054a3a5d
--- /dev/null
+++ b/lib/dispatcher/meson.build
@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2023 Ericsson AB
+
+if is_windows
+    build = false
+    reason = 'not supported on Windows'
+    subdir_done()
+endif
+
+sources = files(
+        'rte_dispatcher.c',
+)
+headers = files(
+        'rte_dispatcher.h',
+)
+
+deps += ['eventdev']
diff --git a/lib/dispatcher/rte_dispatcher.c b/lib/dispatcher/rte_dispatcher.c
new file mode 100644
index 0000000000..0e69db2b9b
--- /dev/null
+++ b/lib/dispatcher/rte_dispatcher.c
@@ -0,0 +1,708 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2023 Ericsson AB
+ */
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <rte_branch_prediction.h>
+#include <rte_common.h>
+#include <rte_lcore.h>
+#include <rte_random.h>
+#include <rte_service_component.h>
+
+#include "eventdev_pmd.h"
+
+#include <rte_dispatcher.h>
+
+#define EVD_MAX_PORTS_PER_LCORE 4
+#define EVD_MAX_HANDLERS 32
+#define EVD_MAX_FINALIZERS 16
+#define EVD_AVG_PRIO_INTERVAL 2000
+#define EVD_SERVICE_NAME "dispatcher"
+
+struct rte_dispatcher_lcore_port {
+	uint8_t port_id;
+	uint16_t batch_size;
+	uint64_t timeout;
+};
+
+struct rte_dispatcher_handler {
+	int id;
+	rte_dispatcher_match_t match_fun;
+	void *match_data;
+	rte_dispatcher_process_t process_fun;
+	void *process_data;
+};
+
+struct rte_dispatcher_finalizer {
+	int id;
+	rte_dispatcher_finalize_t finalize_fun;
+	void *finalize_data;
+};
+
+struct rte_dispatcher_lcore {
+	uint8_t num_ports;
+	uint16_t num_handlers;
+	int32_t prio_count;
+	struct rte_dispatcher_lcore_port ports[EVD_MAX_PORTS_PER_LCORE];
+	struct rte_dispatcher_handler handlers[EVD_MAX_HANDLERS];
+	struct rte_dispatcher_stats stats;
+} __rte_cache_aligned;
+
+struct rte_dispatcher {
+	uint8_t event_dev_id;
+	int socket_id;
+	uint32_t service_id;
+	struct rte_dispatcher_lcore lcores[RTE_MAX_LCORE];
+	uint16_t num_finalizers;
+	struct rte_dispatcher_finalizer finalizers[EVD_MAX_FINALIZERS];
+};
+
+static int
+evd_lookup_handler_idx(struct rte_dispatcher_lcore *lcore,
+		       const struct rte_event *event)
+{
+	uint16_t i;
+
+	for (i = 0; i < lcore->num_handlers; i++) {
+		struct rte_dispatcher_handler *handler =
+			&lcore->handlers[i];
+
+		if (handler->match_fun(event, handler->match_data))
+			return i;
+	}
+
+	return -1;
+}
+
+static void
+evd_prioritize_handler(struct rte_dispatcher_lcore *lcore,
+		       int handler_idx)
+{
+	struct rte_dispatcher_handler tmp;
+
+	if (handler_idx == 0)
+		return;
+
+	/* Let the lucky handler "bubble" up the list */
+
+	tmp = lcore->handlers[handler_idx - 1];
+
+	lcore->handlers[handler_idx - 1] = lcore->handlers[handler_idx];
+
+	lcore->handlers[handler_idx] = tmp;
+}
+
+static inline void
+evd_consider_prioritize_handler(struct rte_dispatcher_lcore *lcore,
+				int handler_idx, uint16_t handler_events)
+{
+	lcore->prio_count -= handler_events;
+
+	if (unlikely(lcore->prio_count <= 0)) {
+		evd_prioritize_handler(lcore, handler_idx);
+
+		/*
+		 * Randomize the interval in the unlikely case
+		 * the traffic follow some very strict pattern.
+		 */
+		lcore->prio_count =
+			rte_rand_max(EVD_AVG_PRIO_INTERVAL) +
+			EVD_AVG_PRIO_INTERVAL / 2;
+	}
+}
+
+static inline void
+evd_dispatch_events(struct rte_dispatcher *dispatcher,
+		    struct rte_dispatcher_lcore *lcore,
+		    struct rte_dispatcher_lcore_port *port,
+		    struct rte_event *events, uint16_t num_events)
+{
+	int i;
+	struct rte_event bursts[EVD_MAX_HANDLERS][num_events];
+	uint16_t burst_lens[EVD_MAX_HANDLERS] = { 0 };
+	uint16_t drop_count = 0;
+	uint16_t dispatch_count;
+	uint16_t dispatched = 0;
+
+	for (i = 0; i < num_events; i++) {
+		struct rte_event *event = &events[i];
+		int handler_idx;
+
+		handler_idx = evd_lookup_handler_idx(lcore, event);
+
+		if (unlikely(handler_idx < 0)) {
+			drop_count++;
+			continue;
+		}
+
+		bursts[handler_idx][burst_lens[handler_idx]] = *event;
+		burst_lens[handler_idx]++;
+	}
+
+	dispatch_count = num_events - drop_count;
+
+	for (i = 0; i < lcore->num_handlers &&
+		 dispatched < dispatch_count; i++) {
+		struct rte_dispatcher_handler *handler =
+			&lcore->handlers[i];
+		uint16_t len = burst_lens[i];
+
+		if (len == 0)
+			continue;
+
+		handler->process_fun(dispatcher->event_dev_id, port->port_id,
+				     bursts[i], len, handler->process_data);
+
+		dispatched += len;
+
+		/*
+		 * Safe, since any reshuffling will only involve
+		 * already-processed handlers.
+		 */
+		evd_consider_prioritize_handler(lcore, i, len);
+	}
+
+	lcore->stats.ev_batch_count++;
+	lcore->stats.ev_dispatch_count += dispatch_count;
+	lcore->stats.ev_drop_count += drop_count;
+
+	for (i = 0; i < dispatcher->num_finalizers; i++) {
+		struct rte_dispatcher_finalizer *finalizer =
+			&dispatcher->finalizers[i];
+
+		finalizer->finalize_fun(dispatcher->event_dev_id,
+					port->port_id,
+					finalizer->finalize_data);
+	}
+}
+
+static __rte_always_inline uint16_t
+evd_port_dequeue(struct rte_dispatcher *dispatcher,
+		 struct rte_dispatcher_lcore *lcore,
+		 struct rte_dispatcher_lcore_port *port)
+{
+	uint16_t batch_size = port->batch_size;
+	struct rte_event events[batch_size];
+	uint16_t n;
+
+	n = rte_event_dequeue_burst(dispatcher->event_dev_id, port->port_id,
+				    events, batch_size, port->timeout);
+
+	if (likely(n > 0))
+		evd_dispatch_events(dispatcher, lcore, port, events, n);
+
+	lcore->stats.poll_count++;
+
+	return n;
+}
+
+static __rte_always_inline uint16_t
+evd_lcore_process(struct rte_dispatcher *dispatcher,
+		  struct rte_dispatcher_lcore *lcore)
+{
+	uint16_t i;
+	uint16_t event_count = 0;
+
+	for (i = 0; i < lcore->num_ports; i++) {
+		struct rte_dispatcher_lcore_port *port =
+			&lcore->ports[i];
+
+		event_count += evd_port_dequeue(dispatcher, lcore, port);
+	}
+
+	return event_count;
+}
+
+static int32_t
+evd_process(void *userdata)
+{
+	struct rte_dispatcher *dispatcher = userdata;
+	unsigned int lcore_id = rte_lcore_id();
+	struct rte_dispatcher_lcore *lcore =
+		&dispatcher->lcores[lcore_id];
+	uint64_t event_count;
+
+	event_count = evd_lcore_process(dispatcher, lcore);
+
+	if (unlikely(event_count == 0))
+		return -EAGAIN;
+
+	return 0;
+}
+
+static int
+evd_service_register(struct rte_dispatcher *dispatcher)
+{
+	struct rte_service_spec service = {
+		.callback = evd_process,
+		.callback_userdata = dispatcher,
+		.capabilities = RTE_SERVICE_CAP_MT_SAFE,
+		.socket_id = dispatcher->socket_id
+	};
+	int rc;
+
+	snprintf(service.name, sizeof(service.name), EVD_SERVICE_NAME);
+
+	rc = rte_service_component_register(&service, &dispatcher->service_id);
+
+	if (rc)
+		RTE_EDEV_LOG_ERR("Registration of dispatcher service "
+				 "%s failed with error code %d\n",
+				 service.name, rc);
+
+	return rc;
+}
+
+static int
+evd_service_unregister(struct rte_dispatcher *dispatcher)
+{
+	int rc;
+
+	rc = rte_service_component_unregister(dispatcher->service_id);
+
+	if (rc)
+		RTE_EDEV_LOG_ERR("Unregistration of dispatcher service "
+				 "failed with error code %d\n", rc);
+
+	return rc;
+}
+
+struct rte_dispatcher *
+rte_dispatcher_create(uint8_t event_dev_id)
+{
+	int socket_id;
+	struct rte_dispatcher *dispatcher;
+	int rc;
+
+	socket_id = rte_event_dev_socket_id(event_dev_id);
+
+	dispatcher =
+		rte_malloc_socket("dispatcher", sizeof(struct rte_dispatcher),
+				  RTE_CACHE_LINE_SIZE, socket_id);
+
+	if (dispatcher == NULL) {
+		RTE_EDEV_LOG_ERR("Unable to allocate memory for dispatcher\n");
+		rte_errno = ENOMEM;
+		return NULL;
+	}
+
+	*dispatcher = (struct rte_dispatcher) {
+		.event_dev_id = event_dev_id,
+		.socket_id = socket_id
+	};
+
+	rc = evd_service_register(dispatcher);
+
+	if (rc < 0) {
+		rte_free(dispatcher);
+		rte_errno = -rc;
+		return NULL;
+	}
+
+	return dispatcher;
+}
+
+int
+rte_dispatcher_free(struct rte_dispatcher *dispatcher)
+{
+	int rc;
+
+	if (dispatcher == NULL)
+		return 0;
+
+	rc = evd_service_unregister(dispatcher);
+
+	if (rc)
+		return rc;
+
+	rte_free(dispatcher);
+
+	return 0;
+}
+
+uint32_t
+rte_dispatcher_service_id_get(const struct rte_dispatcher *dispatcher)
+{
+	return dispatcher->service_id;
+}
+
+static int
+lcore_port_index(struct rte_dispatcher_lcore *lcore,
+		 uint8_t event_port_id)
+{
+	uint16_t i;
+
+	for (i = 0; i < lcore->num_ports; i++) {
+		struct rte_dispatcher_lcore_port *port =
+			&lcore->ports[i];
+
+		if (port->port_id == event_port_id)
+			return i;
+	}
+
+	return -1;
+}
+
+int
+rte_dispatcher_bind_port_to_lcore(struct rte_dispatcher *dispatcher,
+				  uint8_t event_port_id, uint16_t batch_size,
+				  uint64_t timeout, unsigned int lcore_id)
+{
+	struct rte_dispatcher_lcore *lcore;
+	struct rte_dispatcher_lcore_port *port;
+
+	lcore =	&dispatcher->lcores[lcore_id];
+
+	if (lcore->num_ports == EVD_MAX_PORTS_PER_LCORE)
+		return -ENOMEM;
+
+	if (lcore_port_index(lcore, event_port_id) >= 0)
+		return -EEXIST;
+
+	port = &lcore->ports[lcore->num_ports];
+
+	*port = (struct rte_dispatcher_lcore_port) {
+		.port_id = event_port_id,
+		.batch_size = batch_size,
+		.timeout = timeout
+	};
+
+	lcore->num_ports++;
+
+	return 0;
+}
+
+int
+rte_dispatcher_unbind_port_from_lcore(struct rte_dispatcher *dispatcher,
+				      uint8_t event_port_id,
+				      unsigned int lcore_id)
+{
+	struct rte_dispatcher_lcore *lcore;
+	int port_idx;
+	struct rte_dispatcher_lcore_port *port;
+	struct rte_dispatcher_lcore_port *last;
+
+	lcore =	&dispatcher->lcores[lcore_id];
+
+	port_idx = lcore_port_index(lcore, event_port_id);
+
+	if (port_idx < 0)
+		return -ENOENT;
+
+	port = &lcore->ports[port_idx];
+	last = &lcore->ports[lcore->num_ports - 1];
+
+	if (port != last)
+		*port = *last;
+
+	lcore->num_ports--;
+
+	return 0;
+}
+
+static struct rte_dispatcher_handler*
+evd_lcore_get_handler_by_id(struct rte_dispatcher_lcore *lcore,
+			    int handler_id)
+{
+	uint16_t i;
+
+	for (i = 0; i < lcore->num_handlers; i++) {
+		struct rte_dispatcher_handler *handler =
+			&lcore->handlers[i];
+
+		if (handler->id == handler_id)
+			return handler;
+	}
+
+	return NULL;
+}
+
+static int
+evd_alloc_handler_id(struct rte_dispatcher *dispatcher)
+{
+	int handler_id = 0;
+	struct rte_dispatcher_lcore *reference_lcore =
+		&dispatcher->lcores[0];
+
+	if (reference_lcore->num_handlers == EVD_MAX_HANDLERS)
+		return -1;
+
+	while (evd_lcore_get_handler_by_id(reference_lcore, handler_id) != NULL)
+		handler_id++;
+
+	return handler_id;
+}
+
+static void
+evd_lcore_install_handler(struct rte_dispatcher_lcore *lcore,
+		    const struct rte_dispatcher_handler *handler)
+{
+	int handler_idx = lcore->num_handlers;
+
+	lcore->handlers[handler_idx] = *handler;
+	lcore->num_handlers++;
+}
+
+static void
+evd_install_handler(struct rte_dispatcher *dispatcher,
+		    const struct rte_dispatcher_handler *handler)
+{
+	int i;
+
+	for (i = 0; i < RTE_MAX_LCORE; i++) {
+		struct rte_dispatcher_lcore *lcore =
+			&dispatcher->lcores[i];
+		evd_lcore_install_handler(lcore, handler);
+	}
+}
+
+int
+rte_dispatcher_register(struct rte_dispatcher *dispatcher,
+			rte_dispatcher_match_t match_fun, void *match_data,
+			rte_dispatcher_process_t process_fun,
+			void *process_data)
+{
+	struct rte_dispatcher_handler handler = {
+		.match_fun = match_fun,
+		.match_data = match_data,
+		.process_fun = process_fun,
+		.process_data = process_data
+	};
+
+	handler.id = evd_alloc_handler_id(dispatcher);
+
+	if (handler.id < 0)
+		return -ENOMEM;
+
+	evd_install_handler(dispatcher, &handler);
+
+	return handler.id;
+}
+
+static int
+evd_lcore_uninstall_handler(struct rte_dispatcher_lcore *lcore,
+			    int handler_id)
+{
+	struct rte_dispatcher_handler *unreg_handler;
+	int handler_idx;
+	uint16_t last_idx;
+
+	unreg_handler = evd_lcore_get_handler_by_id(lcore, handler_id);
+
+	if (unreg_handler == NULL) {
+		RTE_EDEV_LOG_ERR("Invalid handler id %d\n", handler_id);
+		return -EINVAL;
+	}
+
+	handler_idx = unreg_handler - &lcore->handlers[0];
+
+	last_idx = lcore->num_handlers - 1;
+
+	if (handler_idx != last_idx) {
+		/* move all handlers to maintain handler order */
+		int n = last_idx - handler_idx;
+		memmove(unreg_handler, unreg_handler + 1,
+			sizeof(struct rte_dispatcher_handler) * n);
+	}
+
+	lcore->num_handlers--;
+
+	return 0;
+}
+
+static int
+evd_uninstall_handler(struct rte_dispatcher *dispatcher,
+		      int handler_id)
+{
+	unsigned int lcore_id;
+
+	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
+		struct rte_dispatcher_lcore *lcore =
+			&dispatcher->lcores[lcore_id];
+		int rc;
+
+		rc = evd_lcore_uninstall_handler(lcore, handler_id);
+
+		if (rc < 0)
+			return rc;
+	}
+
+	return 0;
+}
+
+int
+rte_dispatcher_unregister(struct rte_dispatcher *dispatcher, int handler_id)
+{
+	int rc;
+
+	rc = evd_uninstall_handler(dispatcher, handler_id);
+
+	return rc;
+}
+
+static struct rte_dispatcher_finalizer*
+evd_get_finalizer_by_id(struct rte_dispatcher *dispatcher,
+		       int handler_id)
+{
+	int i;
+
+	for (i = 0; i < dispatcher->num_finalizers; i++) {
+		struct rte_dispatcher_finalizer *finalizer =
+			&dispatcher->finalizers[i];
+
+		if (finalizer->id == handler_id)
+			return finalizer;
+	}
+
+	return NULL;
+}
+
+static int
+evd_alloc_finalizer_id(struct rte_dispatcher *dispatcher)
+{
+	int finalizer_id = 0;
+
+	while (evd_get_finalizer_by_id(dispatcher, finalizer_id) != NULL)
+		finalizer_id++;
+
+	return finalizer_id;
+}
+
+static struct rte_dispatcher_finalizer *
+evd_alloc_finalizer(struct rte_dispatcher *dispatcher)
+{
+	int finalizer_idx;
+	struct rte_dispatcher_finalizer *finalizer;
+
+	if (dispatcher->num_finalizers == EVD_MAX_FINALIZERS)
+		return NULL;
+
+	finalizer_idx = dispatcher->num_finalizers;
+	finalizer = &dispatcher->finalizers[finalizer_idx];
+
+	finalizer->id = evd_alloc_finalizer_id(dispatcher);
+
+	dispatcher->num_finalizers++;
+
+	return finalizer;
+}
+
+int
+rte_dispatcher_finalize_register(struct rte_dispatcher *dispatcher,
+				 rte_dispatcher_finalize_t finalize_fun,
+				 void *finalize_data)
+{
+	struct rte_dispatcher_finalizer *finalizer;
+
+	finalizer = evd_alloc_finalizer(dispatcher);
+
+	if (finalizer == NULL)
+		return -ENOMEM;
+
+	finalizer->finalize_fun = finalize_fun;
+	finalizer->finalize_data = finalize_data;
+
+	return finalizer->id;
+}
+
+int
+rte_dispatcher_finalize_unregister(struct rte_dispatcher *dispatcher,
+				   int finalizer_id)
+{
+	struct rte_dispatcher_finalizer *unreg_finalizer;
+	int finalizer_idx;
+	uint16_t last_idx;
+
+	unreg_finalizer = evd_get_finalizer_by_id(dispatcher, finalizer_id);
+
+	if (unreg_finalizer == NULL) {
+		RTE_EDEV_LOG_ERR("Invalid finalizer id %d\n", finalizer_id);
+		return -EINVAL;
+	}
+
+	finalizer_idx = unreg_finalizer - &dispatcher->finalizers[0];
+
+	last_idx = dispatcher->num_finalizers - 1;
+
+	if (finalizer_idx != last_idx) {
+		/* move all finalizers to maintain order */
+		int n = last_idx - finalizer_idx;
+		memmove(unreg_finalizer, unreg_finalizer + 1,
+			sizeof(struct rte_dispatcher_finalizer) * n);
+	}
+
+	dispatcher->num_finalizers--;
+
+	return 0;
+}
+
+static int
+evd_set_service_runstate(struct rte_dispatcher *dispatcher, int state)
+{
+	int rc;
+
+	rc = rte_service_component_runstate_set(dispatcher->service_id,
+						state);
+
+	if (rc != 0) {
+		RTE_EDEV_LOG_ERR("Unexpected error %d occurred while setting "
+				 "service component run state to %d\n", rc,
+				 state);
+		RTE_ASSERT(0);
+	}
+
+	return 0;
+}
+
+int
+rte_dispatcher_start(struct rte_dispatcher *dispatcher)
+{
+	return evd_set_service_runstate(dispatcher, 1);
+}
+
+int
+rte_dispatcher_stop(struct rte_dispatcher *dispatcher)
+{
+	return evd_set_service_runstate(dispatcher, 0);
+}
+
+static void
+evd_aggregate_stats(struct rte_dispatcher_stats *result,
+		    const struct rte_dispatcher_stats *part)
+{
+	result->poll_count += part->poll_count;
+	result->ev_batch_count += part->ev_batch_count;
+	result->ev_dispatch_count += part->ev_dispatch_count;
+	result->ev_drop_count += part->ev_drop_count;
+}
+
+void
+rte_dispatcher_stats_get(const struct rte_dispatcher *dispatcher,
+			 struct rte_dispatcher_stats *stats)
+{
+	unsigned int lcore_id;
+
+	*stats = (struct rte_dispatcher_stats) {};
+
+	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
+		const struct rte_dispatcher_lcore *lcore =
+			&dispatcher->lcores[lcore_id];
+
+		evd_aggregate_stats(stats, &lcore->stats);
+	}
+}
+
+void
+rte_dispatcher_stats_reset(struct rte_dispatcher *dispatcher)
+{
+	unsigned int lcore_id;
+
+	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++) {
+		struct rte_dispatcher_lcore *lcore =
+			&dispatcher->lcores[lcore_id];
+
+		lcore->stats = (struct rte_dispatcher_stats) {};
+	}
+}
diff --git a/lib/dispatcher/rte_dispatcher.h b/lib/dispatcher/rte_dispatcher.h
new file mode 100644
index 0000000000..0387316d7b
--- /dev/null
+++ b/lib/dispatcher/rte_dispatcher.h
@@ -0,0 +1,468 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2023 Ericsson AB
+ */
+
+#ifndef __RTE_DISPATCHER_H__
+#define __RTE_DISPATCHER_H__
+
+/**
+ * @file
+ *
+ * RTE Dispatcher
+ *
+ * @warning
+ * @b EXPERIMENTAL:
+ * All functions in this file may be changed or removed without prior notice.
+ *
+ * The purpose of the dispatcher is to help decouple different parts
+ * of an application (e.g., modules), sharing the same underlying
+ * event device.
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <rte_eventdev.h>
+
+/**
+ * Function prototype for match callbacks.
+ *
+ * Match callbacks are used by an application to decide how the
+ * dispatcher distributes events to different parts of the
+ * application.
+ *
+ * The application is not expected to process the event at the point
+ * of the match call. Such matters should be deferred to the process
+ * callback invocation.
+ *
+ * The match callback may be used as an opportunity to prefetch data.
+ *
+ * @param event
+ *  Pointer to event
+ *
+ * @param cb_data
+ *  The pointer supplied by the application in
+ *  rte_dispatcher_register().
+ *
+ * @return
+ *   Returns true in case this events should be delivered (via
+ *   the process callback), and false otherwise.
+ */
+typedef bool
+(*rte_dispatcher_match_t)(const struct rte_event *event, void *cb_data);
+
+/**
+ * Function prototype for process callbacks.
+ *
+ * The process callbacks are used by the dispatcher to deliver
+ * events for processing.
+ *
+ * @param event_dev_id
+ *  The originating event device id.
+ *
+ * @param event_port_id
+ *  The originating event port.
+ *
+ * @param events
+ *  Pointer to an array of events.
+ *
+ * @param num
+ *  The number of events in the @p events array.
+ *
+ * @param cb_data
+ *  The pointer supplied by the application in
+ *  rte_dispatcher_register().
+ */
+
+typedef void
+(*rte_dispatcher_process_t)(uint8_t event_dev_id, uint8_t event_port_id,
+				  struct rte_event *events, uint16_t num,
+				  void *cb_data);
+
+/**
+ * Function prototype for finalize callbacks.
+ *
+ * The finalize callbacks are used by the dispatcher to notify the
+ * application it has delivered all events from a particular batch
+ * dequeued from the event device.
+ *
+ * @param event_dev_id
+ *  The originating event device id.
+ *
+ * @param event_port_id
+ *  The originating event port.
+ *
+ * @param cb_data
+ *  The pointer supplied by the application in
+ *  rte_dispatcher_finalize_register().
+ */
+
+typedef void
+(*rte_dispatcher_finalize_t)(uint8_t event_dev_id, uint8_t event_port_id,
+				   void *cb_data);
+
+/**
+ * Dispatcher statistics
+ */
+struct rte_dispatcher_stats {
+	uint64_t poll_count;
+	/**< Number of event dequeue calls made toward the event device. */
+	uint64_t ev_batch_count;
+	/**< Number of non-empty event batches dequeued from event device.*/
+	uint64_t ev_dispatch_count;
+	/**< Number of events dispatched to a handler.*/
+	uint64_t ev_drop_count;
+	/**< Number of events dropped because no handler was found. */
+};
+
+/**
+ * Create a dispatcher with the specified id.
+ *
+ * @param event_dev_id
+ *  The identifier of the event device from which this dispatcher
+ *  will dequeue events.
+ *
+ * @return
+ *   A pointer to a new dispatcher instance, or NULL on failure, in which
+ *   case rte_errno is set.
+ */
+__rte_experimental
+struct rte_dispatcher *
+rte_dispatcher_create(uint8_t event_dev_id);
+
+/**
+ * Free a dispatcher.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @return
+ *  - 0: Success
+ *  - <0: Error code on failure
+ */
+__rte_experimental
+int
+rte_dispatcher_free(struct rte_dispatcher *dispatcher);
+
+/**
+ * Retrieve the service identifier of a dispatcher.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @return
+ *  The dispatcher service's id.
+ */
+__rte_experimental
+uint32_t
+rte_dispatcher_service_id_get(const struct rte_dispatcher *dispatcher);
+
+/**
+ * Binds an event device port to a specific lcore on the specified
+ * dispatcher.
+ *
+ * This function configures the event port id to be used by the event
+ * dispatcher service, if run on the specified lcore.
+ *
+ * Multiple event device ports may be bound to the same lcore. A
+ * particular port must not be bound to more than one lcore.
+ *
+ * If the dispatcher service is mapped (with rte_service_map_lcore_set())
+ * to a lcore to which no ports are bound, the service function will be a
+ * no-operation.
+ *
+ * This function may be called by any thread (including unregistered
+ * non-EAL threads), but not while the dispatcher is running on lcore
+ * specified by @c lcore_id.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @param event_port_id
+ *  The event device port identifier.
+ *
+ * @param batch_size
+ *  The batch size to use in rte_event_dequeue_burst(), for the
+ *  configured event device port and lcore.
+ *
+ * @param timeout
+ *  The timeout parameter to use in rte_event_dequeue_burst(), for the
+ *  configured event device port and lcore.
+ *
+ * @param lcore_id
+ *  The lcore by which this event port will be used.
+ *
+ * @return
+ *  - 0: Success
+ *  - -ENOMEM: Unable to allocate sufficient resources.
+ *  - -EEXISTS: Event port is already configured.
+ *  - -EINVAL: Invalid arguments.
+ */
+__rte_experimental
+int
+rte_dispatcher_bind_port_to_lcore(struct rte_dispatcher *dispatcher,
+				  uint8_t event_port_id, uint16_t batch_size,
+				  uint64_t timeout, unsigned int lcore_id);
+
+/**
+ * Unbind an event device port from a specific lcore.
+ *
+ * This function may be called by any thread (including unregistered
+ * non-EAL threads), but not while the dispatcher is running on
+ * lcore specified by @c lcore_id.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @param event_port_id
+ *  The event device port identifier.
+ *
+ * @param lcore_id
+ *  The lcore which was using this event port.
+ *
+ * @return
+ *  - 0: Success
+ *  - -ENOENT: Event port id not bound to this @c lcore_id.
+ */
+__rte_experimental
+int
+rte_dispatcher_unbind_port_from_lcore(struct rte_dispatcher *dispatcher,
+				      uint8_t event_port_id,
+				      unsigned int lcore_id);
+
+/**
+ * Register an event handler.
+ *
+ * The match callback function is used to select if a particular event
+ * should be delivered, using the corresponding process callback
+ * function.
+ *
+ * The reason for having two distinct steps is to allow the dispatcher
+ * to deliver all events as a batch. This in turn will cause
+ * processing of a particular kind of events to happen in a
+ * back-to-back manner, improving cache locality.
+ *
+ * The list of handler callback functions is shared among all lcores,
+ * but will only be executed on lcores which has an eventdev port
+ * bound to them, and which are running the dispatcher service.
+ *
+ * An event is delivered to at most one handler. Events where no
+ * handler is found are dropped.
+ *
+ * The application must not depend on the order of which the match
+ * functions are invoked.
+ *
+ * Ordering of events is not guaranteed to be maintained between
+ * different deliver callbacks. For example, suppose there are two
+ * callbacks registered, matching different subsets of events arriving
+ * on an atomic queue. A batch of events [ev0, ev1, ev2] are dequeued
+ * on a particular port, all pertaining to the same flow. The match
+ * callback for registration A returns true for ev0 and ev2, and the
+ * matching function for registration B for ev1. In that scenario, the
+ * dispatcher may choose to deliver first [ev0, ev2] using A's deliver
+ * function, and then [ev1] to B - or vice versa.
+ *
+ * rte_dispatcher_register() may be called by any thread
+ * (including unregistered non-EAL threads), but not while the event
+ * dispatcher is running on any service lcore.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @param match_fun
+ *  The match callback function.
+ *
+ * @param match_cb_data
+ *  A pointer to some application-specific opaque data (or NULL),
+ *  which is supplied back to the application when match_fun is
+ *  called.
+ *
+ * @param process_fun
+ *  The process callback function.
+ *
+ * @param process_cb_data
+ *  A pointer to some application-specific opaque data (or NULL),
+ *  which is supplied back to the application when process_fun is
+ *  called.
+ *
+ * @return
+ *  - >= 0: The identifier for this registration.
+ *  - -ENOMEM: Unable to allocate sufficient resources.
+ */
+__rte_experimental
+int
+rte_dispatcher_register(struct rte_dispatcher *dispatcher,
+			rte_dispatcher_match_t match_fun, void *match_cb_data,
+			rte_dispatcher_process_t process_fun,
+			void *process_cb_data);
+
+/**
+ * Unregister an event handler.
+ *
+ * This function may be called by any thread (including unregistered
+ * non-EAL threads), but not while the dispatcher is running on
+ * any service lcore.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @param handler_id
+ *  The handler registration id returned by the original
+ *  rte_dispatcher_register() call.
+ *
+ * @return
+ *  - 0: Success
+ *  - -EINVAL: The @c handler_id parameter was invalid.
+ */
+__rte_experimental
+int
+rte_dispatcher_unregister(struct rte_dispatcher *dispatcher, int handler_id);
+
+/**
+ * Register a finalize callback function.
+ *
+ * An application may optionally install one or more finalize
+ * callbacks.
+ *
+ * All finalize callbacks are invoked by the dispatcher when a
+ * complete batch of events (retrieve using rte_event_dequeue_burst())
+ * have been delivered to the application (or have been dropped).
+ *
+ * The finalize callback is not tied to any particular handler.
+ *
+ * The finalize callback provides an opportunity for the application
+ * to do per-batch processing. One case where this may be useful is if
+ * an event output buffer is used, and is shared among several
+ * handlers. In such a case, proper output buffer flushing may be
+ * assured using a finalize callback.
+ *
+ * rte_dispatcher_finalize_register() may be called by any thread
+ * (including unregistered non-EAL threads), but not while the
+ * dispatcher is running on any service lcore.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @param finalize_fun
+ *  The function called after completing the processing of a
+ *  dequeue batch.
+ *
+ * @param finalize_data
+ *  A pointer to some application-specific opaque data (or NULL),
+ *  which is supplied back to the application when @c finalize_fun is
+ *  called.
+ *
+ * @return
+ *  - >= 0: The identifier for this registration.
+ *  - -ENOMEM: Unable to allocate sufficient resources.
+ */
+__rte_experimental
+int
+rte_dispatcher_finalize_register(struct rte_dispatcher *dispatcher,
+				 rte_dispatcher_finalize_t finalize_fun,
+				 void *finalize_data);
+
+/**
+ * Unregister a finalize callback.
+ *
+ * This function may be called by any thread (including unregistered
+ * non-EAL threads), but not while the dispatcher is running on
+ * any service lcore.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @param reg_id
+ *  The finalize registration id returned by the original
+ *  rte_dispatcher_finalize_register() call.
+ *
+ * @return
+ *  - 0: Success
+ *  - -EINVAL: The @c reg_id parameter was invalid.
+ */
+__rte_experimental
+int
+rte_dispatcher_finalize_unregister(struct rte_dispatcher *dispatcher,
+				   int reg_id);
+
+/**
+ * Start a dispatcher instance.
+ *
+ * Enables the dispatcher service.
+ *
+ * The underlying event device must have been started prior to calling
+ * rte_dispatcher_start().
+ *
+ * For the dispatcher to actually perform work (i.e., dispatch
+ * events), its service must have been mapped to one or more service
+ * lcores, and its service run state set to '1'. A dispatcher's
+ * service is retrieved using rte_dispatcher_service_id_get().
+ *
+ * Each service lcore to which the dispatcher is mapped should
+ * have at least one event port configured. Such configuration is
+ * performed by calling rte_dispatcher_bind_port_to_lcore(), prior to
+ * starting the dispatcher.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @return
+ *  - 0: Success
+ *  - <0: Error code on failure
+ */
+__rte_experimental
+int
+rte_dispatcher_start(struct rte_dispatcher *dispatcher);
+
+/**
+ * Stop a running dispatcher instance.
+ *
+ * Disables the dispatcher service.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ *
+ * @return
+ *  - 0: Success
+ *  - -EINVAL: Invalid @c id.
+ */
+__rte_experimental
+int
+rte_dispatcher_stop(struct rte_dispatcher *dispatcher);
+
+/**
+ * Retrieve statistics for a dispatcher instance.
+ *
+ * This function is MT safe and may be called by any thread
+ * (including unregistered non-EAL threads).
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ * @param[out] stats
+ *   A pointer to a structure to fill with statistics.
+ */
+__rte_experimental
+void
+rte_dispatcher_stats_get(const struct rte_dispatcher *dispatcher,
+			 struct rte_dispatcher_stats *stats);
+
+/**
+ * Reset statistics for a dispatcher instance.
+ *
+ * This function may be called by any thread (including unregistered
+ * non-EAL threads), but may not produce the correct result if the
+ * dispatcher is running on any service lcore.
+ *
+ * @param dispatcher
+ *  The dispatcher instance.
+ */
+__rte_experimental
+void
+rte_dispatcher_stats_reset(struct rte_dispatcher *dispatcher);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __RTE_DISPATCHER__ */
diff --git a/lib/dispatcher/version.map b/lib/dispatcher/version.map
new file mode 100644
index 0000000000..8f9ad96522
--- /dev/null
+++ b/lib/dispatcher/version.map
@@ -0,0 +1,20 @@
+EXPERIMENTAL {
+	global:
+
+	# added in 23.11
+	rte_dispatcher_create;
+	rte_dispatcher_free;
+	rte_dispatcher_service_id_get;
+	rte_dispatcher_bind_port_to_lcore;
+	rte_dispatcher_unbind_port_from_lcore;
+	rte_dispatcher_register;
+	rte_dispatcher_unregister;
+	rte_dispatcher_finalize_register;
+	rte_dispatcher_finalize_unregister;
+	rte_dispatcher_start;
+	rte_dispatcher_stop;
+	rte_dispatcher_stats_get;
+	rte_dispatcher_stats_reset;
+
+	local: *;
+};
diff --git a/lib/meson.build b/lib/meson.build
index 099b0ed18a..3093b338d2 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -35,6 +35,7 @@ libraries = [
         'distributor',
         'efd',
         'eventdev',
+        'dispatcher', # dispatcher depends on eventdev
         'gpudev',
         'gro',
         'gso',
@@ -81,6 +82,7 @@ optional_libs = [
         'cfgfile',
         'compressdev',
         'cryptodev',
+        'dispatcher',
         'distributor',
         'dmadev',
         'efd',
-- 
2.34.1