[v11,4/4] app/testpmd: add recycle mbufs engine

diff --git a/app/test-pmd/meson.build b/app/test-pmd/meson.build
index d2e3f60892..6e5f067274 100644
--- a/app/test-pmd/meson.build
+++ b/app/test-pmd/meson.build
@@ -22,6 +22,7 @@  sources = files(
         'macswap.c',
         'noisy_vnf.c',
         'parameters.c',
+	'recycle_mbufs.c',
         'rxonly.c',
         'shared_rxq_fwd.c',
         'testpmd.c',
diff --git a/app/test-pmd/recycle_mbufs.c b/app/test-pmd/recycle_mbufs.c
new file mode 100644
index 0000000000..6e9e1c5eb6
--- /dev/null
+++ b/app/test-pmd/recycle_mbufs.c
@@ -0,0 +1,58 @@ 
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (c) 2023 Arm Limited.
+ */
+
+#include "testpmd.h"
+
+/*
+ * Forwarding of packets in I/O mode.
+ * Enable mbufs recycle mode to recycle txq used mbufs
+ * for rxq mbuf ring. This can bypass mempool path and
+ * save CPU cycles.
+ */
+static bool
+pkt_burst_recycle_mbufs(struct fwd_stream *fs)
+{
+	struct rte_mbuf *pkts_burst[MAX_PKT_BURST];
+	uint16_t nb_rx;
+
+	/* Recycle used mbufs from the txq, and move these mbufs into
+	 * the rxq mbuf ring.
+	 */
+	rte_eth_recycle_mbufs(fs->rx_port, fs->rx_queue,
+			fs->tx_port, fs->tx_queue, &(fs->recycle_rxq_info));
+
+	/*
+	 * Receive a burst of packets and forward them.
+	 */
+	nb_rx = common_fwd_stream_receive(fs, pkts_burst, nb_pkt_per_burst);
+	if (unlikely(nb_rx == 0))
+		return false;
+
+	common_fwd_stream_transmit(fs, pkts_burst, nb_rx);
+
+	return true;
+}
+
+static void
+recycle_mbufs_stream_init(struct fwd_stream *fs)
+{
+	int rc;
+
+	/* Retrieve information about given ports's Rx queue
+	 * for recycling mbufs.
+	 */
+	rc = rte_eth_recycle_rx_queue_info_get(fs->rx_port,
+			fs->rx_queue, &(fs->recycle_rxq_info));
+	if (rc != 0)
+		TESTPMD_LOG(WARNING,
+			"Failed to get rx queue mbufs recycle info\n");
+
+	common_fwd_stream_init(fs);
+}
+
+struct fwd_engine recycle_mbufs_engine = {
+	.fwd_mode_name  = "recycle_mbufs",
+	.stream_init    = recycle_mbufs_stream_init,
+	.packet_fwd     = pkt_burst_recycle_mbufs,
+};
diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
index 938ca035d4..5d0f9ca119 100644
--- a/app/test-pmd/testpmd.c
+++ b/app/test-pmd/testpmd.c
@@ -199,6 +199,7 @@  struct fwd_engine * fwd_engines[] = {
 	&icmp_echo_engine,
 	&noisy_vnf_engine,
 	&five_tuple_swap_fwd_engine,
+	&recycle_mbufs_engine,
 #ifdef RTE_LIBRTE_IEEE1588
 	&ieee1588_fwd_engine,
 #endif
diff --git a/app/test-pmd/testpmd.h b/app/test-pmd/testpmd.h
index f1df6a8faf..0eb8d7883a 100644
--- a/app/test-pmd/testpmd.h
+++ b/app/test-pmd/testpmd.h
@@ -188,6 +188,8 @@  struct fwd_stream {
 	struct pkt_burst_stats rx_burst_stats;
 	struct pkt_burst_stats tx_burst_stats;
 	struct fwd_lcore *lcore; /**< Lcore being scheduled. */
+	/**< Rx queue information for recycling mbufs */
+	struct rte_eth_recycle_rxq_info recycle_rxq_info;
 };
 
 /**
@@ -449,6 +451,7 @@  extern struct fwd_engine csum_fwd_engine;
 extern struct fwd_engine icmp_echo_engine;
 extern struct fwd_engine noisy_vnf_engine;
 extern struct fwd_engine five_tuple_swap_fwd_engine;
+extern struct fwd_engine recycle_mbufs_engine;
 #ifdef RTE_LIBRTE_IEEE1588
 extern struct fwd_engine ieee1588_fwd_engine;
 #endif
diff --git a/doc/guides/testpmd_app_ug/run_app.rst b/doc/guides/testpmd_app_ug/run_app.rst
index 6e9c552e76..24a086401e 100644
--- a/doc/guides/testpmd_app_ug/run_app.rst
+++ b/doc/guides/testpmd_app_ug/run_app.rst
@@ -232,6 +232,7 @@  The command line options are:
        noisy
        5tswap
        shared-rxq
+       recycle_mbufs
 
 *   ``--rss-ip``
 
diff --git a/doc/guides/testpmd_app_ug/testpmd_funcs.rst b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
index a182479ab2..aef4de3e0e 100644
--- a/doc/guides/testpmd_app_ug/testpmd_funcs.rst
+++ b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
@@ -318,7 +318,7 @@  set fwd
 Set the packet forwarding mode::
 
    testpmd> set fwd (io|mac|macswap|flowgen| \
-                     rxonly|txonly|csum|icmpecho|noisy|5tswap|shared-rxq) (""|retry)
+                     rxonly|txonly|csum|icmpecho|noisy|5tswap|shared-rxq|recycle_mbufs) (""|retry)
 
 ``retry`` can be specified for forwarding engines except ``rx_only``.
 
@@ -364,6 +364,9 @@  The available information categories are:
 * ``shared-rxq``: Receive only for shared Rx queue.
   Resolve packet source port from mbuf and update stream statistics accordingly.
 
+* ``recycle_mbufs``:  Recycle Tx queue used mbufs for Rx queue mbuf ring.
+  This mode uses fast path mbuf recycle feature and forwards packets in I/O mode.
+
 Example::
 
    testpmd> set fwd rxonly