[PATCH v6 1/2] mempool: add stack (lifo) mempool handler

[David Hunt <david.hunt@intel.com>]

This is a mempool handler that is useful for pipelining apps, where
the mempool cache doesn't really work - example, where we have one
core doing rx (and alloc), and another core doing Tx (and return). In
such a case, the mempool ring simply cycles through all the mbufs,
resulting in a LLC miss on every mbuf allocated when the number of
mbufs is large. A stack recycles buffers more effectively in this
case.

Signed-off-by: David Hunt <david.hunt@intel.com>
---
 lib/librte_mempool/Makefile            |   1 +
 lib/librte_mempool/rte_mempool_stack.c | 145 +++++++++++++++++++++++++++++++++
 2 files changed, 146 insertions(+)
 create mode 100644 lib/librte_mempool/rte_mempool_stack.c

diff --git a/lib/librte_mempool/Makefile b/lib/librte_mempool/Makefile
index a4c089e..057a6ab 100644
--- a/lib/librte_mempool/Makefile
+++ b/lib/librte_mempool/Makefile
@@ -44,6 +44,7 @@ LIBABIVER := 2
 SRCS-$(CONFIG_RTE_LIBRTE_MEMPOOL) +=  rte_mempool.c
 SRCS-$(CONFIG_RTE_LIBRTE_MEMPOOL) +=  rte_mempool_ops.c
 SRCS-$(CONFIG_RTE_LIBRTE_MEMPOOL) +=  rte_mempool_ring.c
+SRCS-$(CONFIG_RTE_LIBRTE_MEMPOOL) +=  rte_mempool_stack.c
 # install includes
 SYMLINK-$(CONFIG_RTE_LIBRTE_MEMPOOL)-include := rte_mempool.h
 
diff --git a/lib/librte_mempool/rte_mempool_stack.c b/lib/librte_mempool/rte_mempool_stack.c
new file mode 100644
index 0000000..a92da69
--- /dev/null
+++ b/lib/librte_mempool/rte_mempool_stack.c
@@ -0,0 +1,145 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2016 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <rte_mempool.h>
+#include <rte_malloc.h>
+
+struct rte_mempool_stack {
+	rte_spinlock_t sl;
+
+	uint32_t size;
+	uint32_t len;
+	void *objs[];
+};
+
+static int
+stack_alloc(struct rte_mempool *mp)
+{
+	struct rte_mempool_stack *s;
+	unsigned n = mp->size;
+	int size = sizeof(*s) + (n+16)*sizeof(void *);
+
+	/* Allocate our local memory structure */
+	s = rte_zmalloc_socket("mempool-stack",
+			size,
+			RTE_CACHE_LINE_SIZE,
+			mp->socket_id);
+	if (s == NULL) {
+		RTE_LOG(ERR, MEMPOOL, "Cannot allocate stack!\n");
+		return -ENOMEM;
+	}
+
+	rte_spinlock_init(&s->sl);
+
+	s->size = n;
+	mp->pool_data = s;
+
+	return 0;
+}
+
+static int stack_enqueue(struct rte_mempool *mp, void * const *obj_table,
+		unsigned n)
+{
+	struct rte_mempool_stack *s = mp->pool_data;
+	void **cache_objs;
+	unsigned index;
+
+	rte_spinlock_lock(&s->sl);
+	cache_objs = &s->objs[s->len];
+
+	/* Is there sufficient space in the stack ? */
+	if ((s->len + n) > s->size) {
+		rte_spinlock_unlock(&s->sl);
+		return -ENOBUFS;
+	}
+
+	/* Add elements back into the cache */
+	for (index = 0; index < n; ++index, obj_table++)
+		cache_objs[index] = *obj_table;
+
+	s->len += n;
+
+	rte_spinlock_unlock(&s->sl);
+	return 0;
+}
+
+static int stack_dequeue(struct rte_mempool *mp, void **obj_table,
+		unsigned n)
+{
+	struct rte_mempool_stack *s = mp->pool_data;
+	void **cache_objs;
+	unsigned index, len;
+
+	rte_spinlock_lock(&s->sl);
+
+	if (unlikely(n > s->len)) {
+		rte_spinlock_unlock(&s->sl);
+		return -ENOENT;
+	}
+
+	cache_objs = s->objs;
+
+	for (index = 0, len = s->len - 1; index < n;
+			++index, len--, obj_table++)
+		*obj_table = cache_objs[len];
+
+	s->len -= n;
+	rte_spinlock_unlock(&s->sl);
+	return n;
+}
+
+static unsigned
+stack_get_count(const struct rte_mempool *mp)
+{
+	struct rte_mempool_stack *s = mp->pool_data;
+
+	return s->len;
+}
+
+static void
+stack_free(struct rte_mempool *mp)
+{
+	rte_free((void *)(mp->pool_data));
+}
+
+static struct rte_mempool_ops ops_stack = {
+	.name = "stack",
+	.alloc = stack_alloc,
+	.free = stack_free,
+	.enqueue = stack_enqueue,
+	.dequeue = stack_dequeue,
+	.get_count = stack_get_count
+};
+
+MEMPOOL_REGISTER_OPS(ops_stack);
-- 
2.5.5