initial tle_dring implementation

The Dynamic Ring (dring) is a implementation of unbounded FIFO queue,
that supports lockless bulk enqueue/dequeue for multiple producers/consumers.
Internally it contains producer/consumer head/tail indexes
(same as DPDK rte_ring), plus linked list of Dynamic Ring Blocks (drb)s.
Each drb contains some metadata plus array of pointers to queued objects.
It is a caller responsibility to provide sufficient number of drbs for
enqueue operation, and manage unused drbs returned by dequeue operation.
dring features:
- FIFO (First In First Out)
- Lockless implementation.
- Multi- or single-consumer dequeue.
- Multi- or single-producer enqueue.
- Bulk dequeue.
- Bulk enqueue.

Change-Id: I3621c99c6b114a387036a397e79baa8d1588bdb5
Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>

8 files changed, 1207 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index c22527c..072b466 100644
--- a/Makefile
+++ b/Makefile
@@ -26,6 +26,7 @@ RTE_TARGET ?= x86_64-native-linuxapp-gcc
 
 DIRS-y += lib
 DIRS-y += examples
+DIRS-y += test
 
 MAKEFLAGS += --no-print-directory
 
diff --git a/lib/Makefile b/lib/Makefile
index 56e8efb..8ce9bac 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -21,6 +21,7 @@ endif
 
 include $(RTE_SDK)/mk/rte.vars.mk
 
+DIRS-y += libtle_dring
 DIRS-y += libtle_udp
 
 include $(TLDK_ROOT)/mk/tle.subdir.mk
diff --git a/lib/libtle_dring/Makefile b/lib/libtle_dring/Makefile
new file mode 100644
index 0000000..1f2c940
--- /dev/null
+++ b/lib/libtle_dring/Makefile
@@ -0,0 +1,38 @@
+# Copyright (c) 2016 Intel Corporation.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+ifeq ($(RTE_SDK),)
+$(error "Please define RTE_SDK environment variable")
+endif
+
+# Default target, can be overwritten by command line or environment
+RTE_TARGET ?= x86_64-native-linuxapp-gcc
+
+include $(RTE_SDK)/mk/rte.vars.mk
+
+# library name
+LIB = libtle_dring.a
+
+CFLAGS += -O3
+CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR)
+
+EXPORT_MAP := tle_dring_version.map
+
+LIBABIVER := 1
+
+#source files
+SRCS-y += dring.c
+
+SYMLINK-y-include += tle_dring.h
+
+include $(RTE_SDK)/mk/rte.extlib.mk
diff --git a/lib/libtle_dring/dring.c b/lib/libtle_dring/dring.c
new file mode 100644
index 0000000..e0fae19
--- /dev/null
+++ b/lib/libtle_dring/dring.c
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2016  Intel Corporation.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <tle_dring.h>
+
+static const char *
+str_drb_dummy(const struct tle_dring *dr, const struct tle_drb *db)
+{
+	return (db == &dr->dummy) ? "<dummy>" : "";
+}
+
+static const char *
+str_obj_state(const struct tle_dring *dr, const struct tle_drb *db,
+	uint32_t idx)
+{
+	if (db->start + idx < dr->cons.tail)
+		return "<stale>";
+	else if (db->start + idx >= dr->prod.tail)
+		return "<free>";
+	else
+		return NULL;
+}
+
+static void
+drb_obj_dump(FILE *f, int32_t verb, const struct tle_dring *dr,
+	const struct tle_drb *db, uint32_t idx)
+{
+	const char *st;
+
+	st = str_obj_state(dr, db, idx);
+
+	/* pointer to object is valid, dump it. */
+	if (st == NULL)
+		fprintf(f, "\t\t\t\t%u:%p\n", db->start + idx, db->objs[idx]);
+
+	/* dump in verbose mode only. */
+	else if (verb > 0)
+		fprintf(f, "\t\t\t\t%u:%p%s\n",
+				db->start + idx, db->objs[idx], st);
+}
+
+static void
+drb_dump(FILE *f, int32_t verb, const struct tle_dring *dr,
+	const struct tle_drb *db)
+{
+	uint32_t i;
+
+	fprintf(f, "\t\t@%p%s={\n", db, str_drb_dummy(dr, db));
+	fprintf(f, "\t\t\tnext=%p,\n", db->next);
+	fprintf(f, "\t\t\tsize=%u,\n", db->size);
+	fprintf(f, "\t\t\tstart=%u,\n", db->start);
+
+	fprintf(f, "\t\t\tobjs[]={\n");
+	for (i = 0; i != db->size; i++)
+		drb_obj_dump(f, verb, dr, db, i);
+	fprintf(f, "\t\t\t},\n");
+
+	fprintf(f, "\t\t},\n");
+}
+
+void
+tle_dring_dump(FILE *f, int32_t verb, const struct tle_dring *dr)
+{
+	struct tle_drb *db;
+
+	fprintf(f, "tle_dring@%p={\n", dr);
+	fprintf(f, "\tflags=%#x,\n", dr->flags);
+
+	fprintf(f, "\tprod={,\n");
+	fprintf(f, "\t\thead=%u,\n", dr->prod.head);
+	fprintf(f, "\t\ttail=%u,\n", dr->prod.tail);
+	fprintf(f, "\t\tcrb=%p%s,\n", dr->prod.crb,
+		str_drb_dummy(dr, dr->prod.crb));
+	fprintf(f, "\t},\n");
+
+	fprintf(f, "\tcons={,\n");
+	fprintf(f, "\t\thead=%u,\n", dr->cons.head);
+	fprintf(f, "\t\ttail=%u,\n", dr->cons.tail);
+	fprintf(f, "\t\tcrb=%p%s,\n", dr->cons.crb,
+		str_drb_dummy(dr, dr->cons.crb));
+	fprintf(f, "\t},\n");
+
+	fprintf(f, "\tdrbs[] = {\n");
+	for (db = dr->prod.crb; db != NULL; db = db->next)
+		drb_dump(f, verb, dr, db);
+	fprintf(f, "\t},\n");
+
+	fprintf(f, "};\n");
+}
diff --git a/lib/libtle_dring/tle_dring.h b/lib/libtle_dring/tle_dring.h
new file mode 100644
index 0000000..e89679d
--- /dev/null
+++ b/lib/libtle_dring/tle_dring.h
@@ -0,0 +1,473 @@
+/*
+ * Copyright (c) 2016  Intel Corporation.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _TLE_DRING_H_
+#define _TLE_DRING_H_
+
+#include <string.h>
+
+#include <rte_common.h>
+#include <rte_atomic.h>
+#include <rte_memory.h>
+#include <rte_debug.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @file
+ * TLE dring
+ *
+ * The Dynamic Ring (dring) is a implementation of unbounded FIFO queue,
+ * that supports lockless bulk enqueue/dequeue for multiple producers/consumers.
+ * Internally it is represented by linked list of Dynamic Ring Blocks (drb).
+ * Each drb contains some metadata plus array of pointers to queued objects.
+ * It is a caller responsibility to provide sufficient number of drbs for
+ * enqueue operation, and manage unused drbs returned by dequeue operation.
+ * dring features:
+ *
+ * - FIFO (First In First Out)
+ * - Lockless implementation.
+ * - Multi- or single-consumer dequeue.
+ * - Multi- or single-producer enqueue.
+ * - Bulk dequeue.
+ * - Bulk enqueue.
+ */
+
+/*
+ * RTE_ASSERT was introduced in DPDK 16.07.
+ * For older versions, use RTE_VERIFY.
+ */
+#ifdef RTE_ASSERT
+#define TLE_DRING_ASSERT(exp)	RTE_ASSERT(exp)
+#else
+#define TLE_DRING_ASSERT(exp)	RTE_VERIFY(exp)
+#endif
+
+struct tle_drb {
+	struct tle_drb *next;
+	void *udata;          /**< user data. */
+	uint32_t size;        /**< number of objects in that buffer. */
+	uint32_t start;       /**< start index for that block. */
+	const void *objs[0];
+} __rte_cache_aligned;
+
+struct tle_dring {
+	uint32_t flags;
+	struct  {
+		volatile uint32_t head;         /**< producer head */
+		volatile uint32_t tail;         /**< producer tail */
+		struct tle_drb * volatile crb;  /**< block to enqueue to */
+	} prod __rte_cache_aligned;
+	struct  {
+		volatile uint32_t head;         /**< consumer head */
+		volatile uint32_t tail;         /**< consumer tail */
+		struct tle_drb * volatile crb;  /**< block to dequeue from */
+	} cons __rte_cache_aligned;
+
+	struct tle_drb dummy;  /**< dummy block */
+};
+
+/*
+ * helper routine, to copy objects to/from the ring.
+ */
+static inline void __attribute__((always_inline))
+__tle_dring_copy_objs(const void *dst[], const void * const src[], uint32_t num)
+{
+	uint32_t i;
+
+	for (i = 0; i != RTE_ALIGN_FLOOR(num, 4); i += 4) {
+		dst[i] = src[i];
+		dst[i + 1] = src[i + 1];
+		dst[i + 2] = src[i + 2];
+		dst[i + 3] = src[i + 3];
+	}
+	switch (num % 4) {
+	case 3:
+		dst[i + 2] = src[i + 2];
+	case 2:
+		dst[i + 1] = src[i + 1];
+	case 1:
+		dst[i] = src[i];
+	}
+}
+
+/*
+ * helper routine, to enqueue objects into the ring.
+ */
+static inline uint32_t __attribute__((always_inline))
+__tle_dring_enqueue(struct tle_dring *dr, uint32_t head,
+	const void * const objs[], uint32_t nb_obj,
+	struct tle_drb *drbs[], uint32_t nb_drb)
+{
+	uint32_t i, j, k, n;
+	struct tle_drb *pb;
+
+	pb = dr->prod.crb;
+	i = 0;
+
+	/* fill the current producer block */
+	if (pb->size != 0) {
+		n = head - pb->start;
+		k = RTE_MIN(pb->size - n, nb_obj);
+		__tle_dring_copy_objs(pb->objs + n, objs, k);
+		i += k;
+	}
+
+	/* fill new blocks, if any */
+	j = 0;
+	if (i != nb_obj && nb_drb != 0) {
+
+		do {
+			pb->next = drbs[j];
+			pb = drbs[j];
+			pb->start = head + i;
+			k = RTE_MIN(pb->size, nb_obj - i);
+			__tle_dring_copy_objs(pb->objs, objs + i, k);
+			i += k;
+		} while (++j != nb_drb && i != nb_obj);
+
+		pb->next = NULL;
+
+		/* new procucer current block. */
+		dr->prod.crb = pb;
+	}
+
+	/* we have to enqueue all requested objects. */
+	TLE_DRING_ASSERT(nb_obj == i);
+
+	/* return number of unused blocks. */
+	return nb_drb - j;
+}
+
+/**
+ * Enqueue several objects on the dring (multi-producers safe).
+ * Note that it is a caller responsibility to provide enough drbs
+ * to enqueue all requested objects.
+ *
+ * @param dr
+ *   A pointer to the ring structure.
+ * @param objs
+ *   An array of pointers to objects to enqueue.
+ * @param nb_obj
+ *   The number of objects to add to the dring from the objs[].
+ * @param drbs
+ *   An array of pointers to the drbs that can be used by the dring
+ *   to perform enqueue operation.
+ * @param nb_drb
+ *   at input: number of elements in the drbs[] array.
+ *   at output: number of unused by the dring elements in the drbs[] array.
+ * @return
+ *   - number of enqueued objects.
+ */
+static inline uint32_t
+tle_dring_mp_enqueue(struct tle_dring *dr, const void * const objs[],
+	uint32_t nb_obj, struct tle_drb *drbs[], uint32_t *nb_drb)
+{
+	uint32_t head, next;
+
+	if (nb_obj == 0)
+		return 0;
+
+	/* reserve position inside the ring. */
+	do {
+		head = dr->prod.head;
+		next = head + nb_obj;
+	} while (rte_atomic32_cmpset(&dr->prod.head, head, next) == 0);
+
+	/*
+	 * If there are other enqueues in progress that preceded that one,
+	 * then wait for them to complete
+	 */
+	while (dr->prod.tail != head)
+		rte_pause();
+
+	/* make sure that changes from previous updates are visible. */
+	rte_smp_rmb();
+
+	/* now it is safe to enqueue into the ring. */
+	*nb_drb = __tle_dring_enqueue(dr, head, objs, nb_obj, drbs, *nb_drb);
+
+	/* make new objects visible to the consumer. */
+	rte_smp_wmb();
+	dr->prod.tail = next;
+
+	return nb_obj;
+}
+
+/**
+ * Enqueue several objects on the dring (NOT multi-producers safe).
+ * Note that it is a caller responsibility to provide enough drbs
+ * to enqueue all requested objects.
+ *
+ * @param dr
+ *   A pointer to the ring structure.
+ * @param objs
+ *   An array of pointers to objects to enqueue.
+ * @param nb_obj
+ *   The number of objects to add to the dring from the objs[].
+ * @param drbs
+ *   An array of pointers to the drbs that can be used by the dring
+ *   to perform enqueue operation.
+ * @param nb_drb
+ *   at input: number of elements in the drbs[] array.
+ *   at output: number of unused by the dring elements in the drbs[] array.
+ * @return
+ *   - number of enqueued objects.
+ */
+static inline uint32_t
+tle_dring_sp_enqueue(struct tle_dring *dr, const void * const objs[],
+	uint32_t nb_obj, struct tle_drb *drbs[], uint32_t *nb_drb)
+{
+	uint32_t head, next;
+
+	if (nb_obj == 0)
+		return 0;
+
+	head = dr->prod.head;
+	next = head + nb_obj;
+
+	/* update producer head value. */
+	dr->prod.head = next;
+
+	/* enqueue into the ring. */
+	*nb_drb = __tle_dring_enqueue(dr, head, objs, nb_obj, drbs, *nb_drb);
+
+	/* make new objects visible to the consumer. */
+	rte_smp_wmb();
+	dr->prod.tail = next;
+
+	return nb_obj;
+}
+
+/*
+ * helper routine, to dequeue objects from the ring.
+ */
+static inline uint32_t __attribute__((always_inline))
+__tle_dring_dequeue(struct tle_dring *dr, uint32_t head,
+	const void *objs[], uint32_t nb_obj,
+	struct tle_drb *drbs[], uint32_t nb_drb)
+{
+	uint32_t i, j, k, n;
+	struct tle_drb *pb;
+
+	pb = dr->cons.crb;
+	i = 0;
+
+	/* copy from the current consumer block */
+	if (pb->size != 0) {
+		n = head - pb->start;
+		k = RTE_MIN(pb->size - n, nb_obj);
+		__tle_dring_copy_objs(objs, pb->objs + n, k);
+		i += k;
+	}
+
+	/* copy from other blocks */
+	j = 0;
+	if (i != nb_obj && nb_drb != 0) {
+
+		do {
+			/* current block is empty, put it into the free list. */
+			if (pb != &dr->dummy)
+				drbs[j++] = pb;
+
+			/* proceed to the next block. */
+			pb = pb->next;
+			k = RTE_MIN(pb->size, nb_obj - i);
+			__tle_dring_copy_objs(objs + i, pb->objs, k);
+			i += k;
+		} while (j != nb_drb && i != nb_obj);
+
+		/* new consumer currect block. */
+		dr->cons.crb = pb;
+	}
+
+	/* we have to dequeue all requested objects. */
+	TLE_DRING_ASSERT(nb_obj == i);
+
+	/* return number of blocks to free. */
+	return j;
+}
+
+/**
+ * Dequeue several objects from the dring (multi-consumers safe).
+ * Note, that it is a caller responsibility to provide drbs[] large
+ * enough to store pointers to all drbs that might become unused
+ * after that dequeue operation. It is a caller responsibility to manage
+ * unused drbs after the dequeue operation is completed
+ * (i.e mark them as free/reusable again, etc.).
+ *
+ * @param dr
+ *   A pointer to the ring structure.
+ * @param objs
+ *   An array of pointers to objects that will be dequeued.
+ * @param nb_obj
+ *   The number of objects to dequeue from the dring.
+ * @param drbs
+ *   An array of pointers to the drbs that will become unused after that
+ *   dequeue operation.
+ * @param nb_drb
+ *   at input: number of elements in the drbs[] array.
+ *   at output: number of filled entries in the drbs[] array.
+ * @return
+ *   - number of dequeued objects.
+ */
+static inline uint32_t
+tle_dring_mc_dequeue(struct tle_dring *dr, const void *objs[], uint32_t nb_obj,
+	struct tle_drb *drbs[], uint32_t *nb_drb)
+{
+	uint32_t head, next, num, tail;
+
+	/* move cons.head atomically */
+	do {
+		head = dr->cons.head;
+		tail = dr->prod.tail;
+
+		num = RTE_MIN(tail - head, nb_obj);
+
+		/* no objects to dequeue */
+		if (num == 0) {
+			*nb_drb = 0;
+			return 0;
+		}
+
+		next = head + num;
+	} while (rte_atomic32_cmpset(&dr->cons.head, head, next) == 0);
+
+	/*
+	 * If there are other dequeues in progress that preceded that one,
+	 * then wait for them to complete
+	 */
+	 while (dr->cons.tail != head)
+		rte_pause();
+
+	/* make sure that changes from previous updates are visible. */
+	rte_smp_rmb();
+
+	/* now it is safe to dequeue from the ring. */
+	*nb_drb = __tle_dring_dequeue(dr, head, objs, num, drbs, *nb_drb);
+
+	/* update consumer tail value. */
+	rte_smp_wmb();
+	dr->cons.tail = next;
+
+	return num;
+}
+
+/**
+ * Dequeue several objects from the dring (NOT multi-consumers safe).
+ * Note, that it is a caller responsibility to provide drbs[] large
+ * enough to store pointers to all drbs that might become unused
+ * after that dequeue operation. It is a caller responsibility to manage
+ * unused drbs after the dequeue operation is completed
+ * (i.e mark them as free/reusable again, etc.).
+ *
+ * @param dr
+ *   A pointer to the ring structure.
+ * @param objs
+ *   An array of pointers to objects that will be dequeued.
+ * @param nb_obj
+ *   The number of objects to dequeue from the dring.
+ * @param drbs
+ *   An array of pointers to the drbs that will become unused after that
+ *   dequeue operation.
+ * @param nb_drb
+ *   at input: number of elements in the drbs[] array.
+ *   at output: number of filled entries in the drbs[] array.
+ * @return
+ *   - number of dequeued objects.
+ */
+static inline uint32_t
+tle_dring_sc_dequeue(struct tle_dring *dr, const void *objs[], uint32_t nb_obj,
+	struct tle_drb *drbs[], uint32_t *nb_drb)
+{
+	uint32_t head, next, num, tail;
+
+	head = dr->cons.head;
+	tail = dr->prod.tail;
+
+	num = RTE_MIN(tail - head, nb_obj);
+
+	/* no objects to dequeue */
+	if (num == 0) {
+		*nb_drb = 0;
+		return 0;
+	}
+
+	next = head + num;
+
+	/* update consumer head value. */
+	dr->cons.head = next;
+
+	/* dequeue from the ring. */
+	*nb_drb = __tle_dring_dequeue(dr, head, objs, num, drbs, *nb_drb);
+
+	/* update consumer tail value. */
+	rte_smp_wmb();
+	dr->cons.tail = next;
+
+	return num;
+}
+
+/**
+ * Reset given dring to the initial state.
+ * Note, that information about all queued objects will be lost.
+ *
+ * @param dr
+ *   A pointer to the dring structure.
+ */
+static inline void
+tle_dring_reset(struct tle_dring *dr)
+{
+	memset(dr, 0, sizeof(*dr));
+	dr->prod.crb = &dr->dummy;
+	dr->cons.crb = &dr->dummy;
+}
+
+/**
+ * Calculate required size for drb to store up to *num* objects.
+ *
+ * @param num
+ *   Number of objects drb should be able to store.
+ * @return
+ *   - required size of the drb.
+ */
+static inline size_t
+tle_drb_calc_size(uint32_t num)
+{
+	size_t sz;
+
+	sz = offsetof(struct tle_drb, objs[num]);
+	return RTE_ALIGN_CEIL(sz, RTE_CACHE_LINE_SIZE);
+}
+
+/**
+ * Dump information about the dring to the file.
+ *
+ * @param f
+ *   A pointer to the file.
+ * @param verb
+ *   Verbosity level (currently only 0 or 1).
+ * @param dr
+ *   A pointer to the dring structure.
+ */
+extern void tle_dring_dump(FILE *f, int32_t verb, const struct tle_dring *dr);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _TLE_DRING_H_ */
diff --git a/test/Makefile b/test/Makefile
new file mode 100644
index 0000000..fb446b4
--- /dev/null
+++ b/test/Makefile
@@ -0,0 +1,26 @@
+# Copyright (c) 2016 Intel Corporation.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+ifeq ($(RTE_SDK),)
+$(error "Please define RTE_SDK environment variable")
+endif
+
+ifeq ($(TLDK_ROOT),)
+$(error "Please define TLDK_SDK environment variable")
+endif
+
+include $(RTE_SDK)/mk/rte.vars.mk
+
+DIRS-y += dring
+
+include $(TLDK_ROOT)/mk/tle.subdir.mk
diff --git a/test/dring/Makefile b/test/dring/Makefile
new file mode 100644
index 0000000..6822a1f
--- /dev/null
+++ b/test/dring/Makefile
@@ -0,0 +1,42 @@
+# Copyright (c) 2016 Intel Corporation.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+ifeq ($(RTE_SDK),)
+$(error "Please define RTE_SDK environment variable")
+endif
+
+ifeq ($(RTE_TARGET),)
+$(error "Please define RTE_TARGET environment variable")
+endif
+
+ifeq ($(TLDK_ROOT),)
+$(error "Please define TLDK_ROOT environment variable")
+endif
+
+include $(RTE_SDK)/mk/rte.vars.mk
+
+# binary name
+APP = test_dring
+
+# all source are stored in SRCS-y
+SRCS-y += test_dring.c
+
+CFLAGS += $(WERROR_FLAGS)
+CFLAGS += -I$(TLDK_ROOT)/$(RTE_TARGET)/include
+
+LDLIBS += -L$(TLDK_ROOT)/$(RTE_TARGET)/lib
+LDLIBS += -ltle_dring
+
+EXTRA_CFLAGS += -O3
+
+include $(RTE_SDK)/mk/rte.extapp.mk
diff --git a/test/dring/test_dring.c b/test/dring/test_dring.c
new file mode 100644
index 0000000..22d0db4
--- /dev/null
+++ b/test/dring/test_dring.c
@@ -0,0 +1,525 @@
+/*
+ * Copyright (c) 2016  Intel Corporation.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <string.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <errno.h>
+
+#include <rte_common.h>
+#include <rte_log.h>
+#include <rte_errno.h>
+#include <rte_launch.h>
+#include <rte_cycles.h>
+#include <rte_eal.h>
+#include <rte_per_lcore.h>
+#include <rte_lcore.h>
+#include <rte_ring.h>
+#include <tle_dring.h>
+#include <rte_random.h>
+
+#define OBJ_NUM		UINT16_MAX
+#define ITER_NUM	(4 * OBJ_NUM)
+
+enum {
+	NONE,
+	SINGLE,
+	MULTI,
+};
+
+struct dring_arg {
+	struct tle_dring *dr;
+	struct rte_ring *r;
+	uint32_t iter;
+	int32_t enq_type;
+	int32_t deq_type;
+	uint32_t enq;
+	uint32_t deq;
+};
+
+/*
+ * free memory allocated for drbs and for the ring itself.
+ */
+static void
+fini_drb_ring(struct rte_ring *r)
+{
+	struct tle_drb *drb;
+
+	/* free drbs. */
+	while (rte_ring_dequeue(r, (void **)&drb) == 0)
+		free(drb);
+
+	/* free ring. */
+	free(r);
+}
+
+/*
+ * allocate drbs for specified number of objects, put them into the ring.
+ */
+static struct rte_ring *
+init_drb_ring(uint32_t num)
+{
+	uint32_t i, k, n;
+	size_t sz, tsz;
+	struct rte_ring *r;
+	struct tle_drb *drb;
+
+	/* allocate and initialise rte_ring. */
+
+	n = rte_align32pow2(num);
+	sz =  sizeof(*r) + n * sizeof(r->ring[0]);
+
+	r = calloc(1, sz);
+	if (r == NULL) {
+		printf("%s:%d(%u) failed to allocate %zu bytes;\n",
+			__func__, __LINE__, num, sz);
+		return NULL;
+	}
+
+	rte_ring_init(r, __func__, n, 0);
+
+	/* allocate drbs and put them into the ring. */
+
+	tsz = sz;
+	for (i = 0; i != num; i += k) {
+		k =  rte_rand() % (UINT8_MAX + 1) + 1;
+		k = RTE_MIN(k, num - i);
+		sz = tle_drb_calc_size(k);
+		drb = calloc(1, sz);
+		if (drb == NULL) {
+			printf("%s:%d(%u) %u-th iteration: "
+				"failed to allocate %zu bytes;\n",
+				__func__, __LINE__, num, i, sz);
+			fini_drb_ring(r);
+			return NULL;
+		}
+		drb->size = k;
+		rte_ring_enqueue(r, drb);
+		tsz += sz;
+	}
+
+	printf("%s(%u) total %zu bytes allocated, number of drbs: %u;\n",
+		__func__, num, tsz, rte_ring_count(r));
+	return r;
+}
+
+/*
+ * Each enqueued object will contain:
+ * [2-3]B: it's own sequence number.
+ * [0-1]B: next object sequence number, or UINT16_MAX.
+ */
+static void
+test_fill_obj(uintptr_t obj[], uint32_t num)
+{
+	uint32_t i;
+
+	for (i = 0; i != num - 1; i++)
+		obj[i] = i << 16 | (i + 1);
+
+	obj[i] = i << 16 | UINT16_MAX;
+}
+
+static uint32_t
+test_check_obj(uintptr_t obj[], uint32_t num)
+{
+	uint32_t i, h, l, oh, ol;
+
+	h = obj[0] >> 16;
+	l = obj[0] & UINT16_MAX;
+
+	if (h + 1 != l && l != UINT16_MAX)
+		return 0;
+
+	if (l == UINT16_MAX)
+		l = 0;
+
+	for (i = 1; i != num; i++) {
+
+		oh = obj[i] >> 16;
+		ol = obj[i] & UINT16_MAX;
+
+		if (l != oh || (oh + 1 != ol && ol != UINT16_MAX))
+			return i;
+
+		l = ol;
+		if (l == UINT16_MAX)
+			l = 0;
+	}
+
+	return num;
+}
+
+static int
+test_dring_dequeue(struct tle_dring *dr, struct rte_ring *r, uint32_t num,
+	int32_t type)
+{
+	uint32_t i, k, lc, n, t;
+	struct tle_drb *drb[num];
+	uintptr_t obj[num];
+
+	lc = rte_lcore_id();
+	k = num;
+
+	/* dequeue objects. */
+	if (type == SINGLE)
+		n = tle_dring_sc_dequeue(dr, (const void **)obj, num, drb, &k);
+	else if (type == MULTI)
+		n = tle_dring_mc_dequeue(dr, (const void **)obj, num, drb, &k);
+	else
+		return -EINVAL;
+
+	if (n == 0)
+		return 0;
+
+	/* check the data returned. */
+	t = test_check_obj(obj, n);
+	if (t != n) {
+		printf("%s:%d(%p, %u) at lcore %u: invalid dequeued object, "
+			"n=%u, idx=%u, obj=%#x, prev obj=%#x;\n",
+			__func__, __LINE__, dr, num, lc, n, t,
+			(uint32_t)obj[t], (t == 0) ? 0 : (uint32_t)obj[t - 1]);
+		return -EFAULT;
+	}
+
+	/* check and free drbs. */
+	for (i = 0; i != k; i++) {
+		/* udata value for drb in use shouldn't be zero. */
+		if (drb[i]->udata == NULL) {
+			printf("error @ %s:%d(%p, %u) at lcore %u: "
+				"erroneous drb@%p={udata=%p, size=%u,};\n",
+				__func__, __LINE__, dr, num, lc, drb[i],
+				drb[i]->udata, drb[i]->size);
+			return -EFAULT;
+		}
+		drb[i]->udata = NULL;
+		rte_ring_enqueue(r, drb[i]);
+	}
+
+	return n;
+}
+
+static int
+test_dring_enqueue(struct tle_dring *dr, struct rte_ring *r, uint32_t num,
+	int32_t type)
+{
+	uint32_t i, j, k, lc, nb;
+	struct tle_drb *drb[num];
+	uintptr_t obj[num];
+
+	lc = rte_lcore_id();
+
+	/* prepare drbs to enqueue up to *num* objects. */
+	for (i = 0, j = 0; i != num; i += k, j++) {
+
+		if (rte_ring_dequeue(r, (void **)&drb[j]) != 0)
+			break;
+
+		/* udata value for unused drb should be zero. */
+		if (drb[j]->udata != NULL) {
+			printf("error @ %s:%d(%p, %u) at lcore %u: "
+				"erroneous drb@%p={udata=%p, size=%u,};\n",
+				__func__, __LINE__, dr, num, lc, drb[j],
+				drb[j]->udata, drb[j]->size);
+			return -EFAULT;
+		}
+
+		/* update udata value with current lcore id. */
+		drb[j]->udata = (void *)(uintptr_t)(lc + 1);
+		k = drb[j]->size;
+		k = RTE_MIN(k, num - i);
+	}
+
+	/* no free drbs left. */
+	if (i == 0)
+		return 0;
+
+	/* fill objects to enqueue. */
+	test_fill_obj(obj, i);
+
+	/* enqueue into the dring. */
+	nb = j;
+	if (type == SINGLE)
+		k = tle_dring_sp_enqueue(dr, (const void **)obj, i, drb, &nb);
+	else if (type == MULTI)
+		k = tle_dring_mp_enqueue(dr, (const void **)obj, i, drb, &nb);
+	else
+		return -EINVAL;
+
+	if (k != i) {
+		printf("%s:%d(%p, %p, %u): failed to enqueue %u objects;\n",
+			__func__, __LINE__, dr, r, num, i);
+	}
+
+	/* free unused drbs */
+	for (i = j - nb; i != j; i++) {
+		if ((uintptr_t)drb[i]->udata != lc + 1) {
+			printf("error @ %s:%d(%p, %u) at lcore %u: "
+				"erroneous drb@%p={udata=%p, size=%u,};\n",
+				__func__, __LINE__, dr, num, lc, drb[i],
+				drb[i]->udata, drb[i]->size);
+			return -EFAULT;
+		}
+		drb[i]->udata = NULL;
+		rte_ring_enqueue(r, drb[i]);
+	}
+
+	return k;
+}
+
+static int
+test_dring_enq_deq(struct dring_arg *arg)
+{
+	int32_t rc;
+	uint32_t i, lc, n;
+
+	rc = 0;
+	arg->enq = 0;
+	arg->deq = 0;
+	lc = rte_lcore_id();
+
+	for (i = 0; i != arg->iter; i++) {
+
+		/* try to enqueue random number of objects. */
+		if (arg->enq_type != NONE) {
+			n = rte_rand() % (UINT8_MAX + 1);
+			rc = test_dring_enqueue(arg->dr, arg->r, n,
+				arg->enq_type);
+			if (rc < 0)
+				break;
+			arg->enq += rc;
+		}
+
+		/* try to dequeue random number of objects. */
+		if (arg->deq_type != NONE) {
+			n = rte_rand() % (UINT8_MAX + 1);
+			rc = test_dring_dequeue(arg->dr, arg->r, n,
+				arg->deq_type);
+			if (rc < 0)
+				break;
+			arg->deq += rc;
+		}
+	}
+
+	if (rc < 0)
+		return rc;
+
+	/* dequeue remaining objects. */
+	while (arg->deq_type != NONE && arg->enq != arg->deq) {
+
+		/* try to dequeue random number of objects. */
+		n = rte_rand() % (UINT8_MAX + 1) + 1;
+		rc = test_dring_dequeue(arg->dr, arg->r, n, arg->deq_type);
+		if (rc <= 0)
+			break;
+		arg->deq += rc;
+	}
+
+	printf("%s:%d(lcore=%u, enq_type=%d, deq_type=%d): "
+		"%u objects enqueued, %u objects dequeued\n",
+		__func__, __LINE__, lc, arg->enq_type, arg->deq_type,
+		arg->enq, arg->deq);
+	return 0;
+}
+
+/*
+ * enqueue/dequeue by single thread.
+ */
+static int
+test_dring_st(void)
+{
+	int32_t rc;
+	struct rte_ring *r;
+	struct tle_dring dr;
+	struct dring_arg arg;
+
+	printf("%s started;\n", __func__);
+
+	tle_dring_reset(&dr);
+	r = init_drb_ring(OBJ_NUM);
+	if (r == NULL)
+		return -ENOMEM;
+
+	tle_dring_dump(stdout, 1, &dr);
+
+	memset(&arg, 0, sizeof(arg));
+	arg.dr = &dr;
+	arg.r = r;
+	arg.iter = ITER_NUM;
+	arg.enq_type = SINGLE;
+	arg.deq_type = SINGLE;
+	rc = test_dring_enq_deq(&arg);
+
+	rc = (rc != 0) ? rc : (arg.enq != arg.deq);
+	printf("%s finished with status: %s(%d);\n",
+		__func__, strerror(-rc), rc);
+
+	tle_dring_dump(stdout, rc != 0, &dr);
+	fini_drb_ring(r);
+
+	return rc;
+}
+
+static int
+test_dring_worker(void *arg)
+{
+	struct dring_arg *p;
+
+	p = (struct dring_arg *)arg;
+	return test_dring_enq_deq(p);
+}
+
+/*
+ * enqueue/dequeue by multiple threads.
+ */
+static int
+test_dring_mt(int32_t master_enq_type, int32_t master_deq_type,
+	int32_t slave_enq_type, int32_t slave_deq_type)
+{
+	int32_t rc;
+	uint32_t lc;
+	uint64_t deq, enq;
+	struct rte_ring *r;
+	struct tle_dring dr;
+	struct dring_arg arg[RTE_MAX_LCORE];
+
+	tle_dring_reset(&dr);
+	r = init_drb_ring(OBJ_NUM);
+	if (r == NULL)
+		return -ENOMEM;
+
+	memset(arg, 0, sizeof(arg));
+
+	/* launch on all slaves */
+	RTE_LCORE_FOREACH_SLAVE(lc) {
+		arg[lc].dr = &dr;
+		arg[lc].r = r;
+		arg[lc].iter = ITER_NUM;
+		arg[lc].enq_type = slave_enq_type;
+		arg[lc].deq_type = slave_deq_type;
+		rte_eal_remote_launch(test_dring_worker, &arg[lc], lc);
+	}
+
+	/* launch on master */
+	lc = rte_lcore_id();
+	arg[lc].dr = &dr;
+	arg[lc].r = r;
+	arg[lc].iter = ITER_NUM;
+	arg[lc].enq_type = master_enq_type;
+	arg[lc].deq_type = master_deq_type;
+	rc = test_dring_worker(&arg[lc]);
+	enq = arg[lc].enq;
+	deq = arg[lc].deq;
+
+	/* wait for slaves. */
+	RTE_LCORE_FOREACH_SLAVE(lc) {
+		rc |= rte_eal_wait_lcore(lc);
+		enq += arg[lc].enq;
+		deq += arg[lc].deq;
+	}
+
+	printf("%s:%d: total %" PRIu64 " objects enqueued, %"
+		PRIu64 " objects dequeued\n",
+		__func__, __LINE__, enq, deq);
+
+	rc = (rc != 0) ? rc : (enq != deq);
+	if (rc != 0)
+		tle_dring_dump(stdout, 1, &dr);
+
+	fini_drb_ring(r);
+	return rc;
+}
+
+static int
+test_dring_mp_mc(void)
+{
+	int32_t rc;
+
+	printf("%s started;\n", __func__);
+	rc = test_dring_mt(MULTI, MULTI, MULTI, MULTI);
+	printf("%s finished with status: %s(%d);\n",
+		__func__, strerror(-rc), rc);
+	return rc;
+}
+
+static int
+test_dring_mp_sc(void)
+{
+	int32_t rc;
+
+	printf("%s started;\n", __func__);
+	rc = test_dring_mt(MULTI, SINGLE, MULTI, NONE);
+	printf("%s finished with status: %s(%d);\n",
+		__func__, strerror(-rc), rc);
+	return rc;
+}
+
+static int
+test_dring_sp_mc(void)
+{
+	int32_t rc;
+
+	printf("%s started;\n", __func__);
+	rc = test_dring_mt(SINGLE, MULTI, NONE, MULTI);
+	printf("%s finished with status: %s(%d);\n",
+		__func__, strerror(-rc), rc);
+	return rc;
+}
+
+static int
+test_dring(void)
+{
+	int32_t rc;
+
+	rc = test_dring_st();
+	if (rc != 0)
+		return rc;
+
+	rc = test_dring_mp_mc();
+	if (rc != 0)
+		return rc;
+
+	rc = test_dring_mp_sc();
+	if (rc != 0)
+		return rc;
+
+	rc = test_dring_sp_mc();
+	if (rc != 0)
+		return rc;
+
+	return 0;
+}
+
+int
+main(int argc, char *argv[])
+{
+	int32_t rc;
+
+	rc = rte_eal_init(argc, argv);
+	if (rc < 0)
+		rte_exit(EXIT_FAILURE,
+			"%s: rte_eal_init failed with error code: %d\n",
+			__func__, rc);
+
+	rc = test_dring();
+	if (rc != 0)
+		printf("TEST FAILED\n");
+	else
+		printf("TEST OK\n");
+
+	return rc;
+}