Re: [dpdk-dev] [PATCH v5] app/testpmd: add forwarding mode to simulate a noisy neighbour

[Kevin Traynor <ktraynor@redhat.com>]

On 08/10/2018 03:49 PM, Jens Freimann wrote:
> This adds a new forwarding mode to testpmd to simulate
> more realistic behavior of a guest machine engaged in receiving
> and sending packets performing Virtual Network Function (VNF).
> 

Hi Jens, comments below,

thanks,
Kevin.

> The goal is to enable a simple way of measuring performance impact on
> cache and memory footprint utilization from various VNF co-located on
> the same host machine. For this it does:
> 
> * Buffer packets in a FIFO:
> 
> Create a fifo to buffer received packets. Once it flows over put
> those packets into the actual tx queue. The fifo is created per tx
> queue and its size can be set with the --buffersize-before-sending
> commandline parameter.

--noisy-tx-sw-buffer-flushtime

> 
> A second commandline parameter is used to set a timeout in
> milliseconds after which the fifo is flushed.
> 
> --noisy-tx-sw-buffer-size [packet numbers]
> Keep the mbuf in a FIFO and forward the over flooding packets from the
> FIFO. This queue is per TX-queue (after all other packet processing).
> 
> --noisy-tx-sw-buffer-flushtime [delay]
> Flush the packet queue if no packets have been seen during
> [delay]. As long as packets are seen, the timer is reset.
> 
> Add several options to simulate route lookups (memory reads) in tables
> that can be quite large, as well as route hit statistics update.
> These options simulates the while stack traversal and
> will trash the cache. Memory access is random.
> 
> * simulate route lookups:
> 
> Allocate a buffer and perform reads and writes on it as specified by
> commandline options:
> 
> --noisy-lkup-memory [size]
> Size of the VNF internal memory (MB), in which the random
> read/write will be done, allocated by rte_malloc (hugepages).
> 
> --noisy-lkup-num-writes [num]
> Number of random writes in memory per packet should be
> performed, simulating hit-flags update. 64 bits per write,
> all write in different cache lines.
> 
> --noisy-lkup-num-reads [num]
> Number of random reads in memory per packet should be
> performed, simulating FIB/table lookups. 64 bits per read,
> all write in different cache lines.
> 
> --noisy-lkup-num-reads-writes [num]
> Number of random reads and writes in memory per packet should
> be performed, simulating stats update. 64 bits per read-write, all
> reads and writes in different cache lines.
> 
> Signed-off-by: Jens Freimann <jfreimann@redhat.com>
> ---
>  app/test-pmd/Makefile                       |   1 +
>  app/test-pmd/meson.build                    |   1 +
>  app/test-pmd/noisy_vnf.c                    | 269 ++++++++++++++++++++++++++++
>  app/test-pmd/parameters.c                   |  60 +++++++
>  app/test-pmd/testpmd.c                      |  35 ++++
>  app/test-pmd/testpmd.h                      |  10 ++
>  doc/guides/testpmd_app_ug/run_app.rst       |  33 ++++
>  doc/guides/testpmd_app_ug/testpmd_funcs.rst |   7 +-
>  8 files changed, 414 insertions(+), 2 deletions(-)
>  create mode 100644 app/test-pmd/noisy_vnf.c
> 
> diff --git a/app/test-pmd/Makefile b/app/test-pmd/Makefile
> index 2b4d604..e2581ca 100644
> --- a/app/test-pmd/Makefile
> +++ b/app/test-pmd/Makefile
> @@ -33,6 +33,7 @@ SRCS-y += rxonly.c
>  SRCS-y += txonly.c
>  SRCS-y += csumonly.c
>  SRCS-y += icmpecho.c
> +SRCS-y += noisy_vnf.c
>  SRCS-$(CONFIG_RTE_LIBRTE_IEEE1588) += ieee1588fwd.c
>  SRCS-$(CONFIG_RTE_LIBRTE_BPF) += bpf_cmd.c
>  
> diff --git a/app/test-pmd/meson.build b/app/test-pmd/meson.build
> index a0b3be0..9ef6ed9 100644
> --- a/app/test-pmd/meson.build
> +++ b/app/test-pmd/meson.build
> @@ -17,6 +17,7 @@ sources = files('cmdline.c',
>  	'iofwd.c',
>  	'macfwd.c',
>  	'macswap.c',
> +	'noisy_vnf.c',
>  	'parameters.c',
>  	'rxonly.c',
>  	'testpmd.c',
> diff --git a/app/test-pmd/noisy_vnf.c b/app/test-pmd/noisy_vnf.c
> new file mode 100644
> index 0000000..dcde7d0
> --- /dev/null
> +++ b/app/test-pmd/noisy_vnf.c
> @@ -0,0 +1,269 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2018 Red Hat Corp.
> + */
> +
> +#include <stdarg.h>
> +#include <stdio.h>
> +#include <stdbool.h>
> +#include <string.h>
> +#include <errno.h>
> +#include <stdint.h>
> +#include <unistd.h>
> +#include <inttypes.h>
> +
> +#include <sys/queue.h>
> +#include <sys/stat.h>
> +
> +#include <rte_common.h>
> +#include <rte_log.h>
> +#include <rte_debug.h>
> +#include <rte_cycles.h>
> +#include <rte_memory.h>
> +#include <rte_launch.h>
> +#include <rte_eal.h>
> +#include <rte_per_lcore.h>
> +#include <rte_lcore.h>
> +#include <rte_memcpy.h>
> +#include <rte_mempool.h>
> +#include <rte_mbuf.h>
> +#include <rte_ethdev.h>
> +#include <rte_flow.h>
> +#include <rte_malloc.h>
> +
> +#include "testpmd.h"
> +
> +struct noisy_config {
> +	struct rte_ring *f;
> +	uint64_t prev_time;
> +	char *vnf_mem;
> +	bool do_buffering;
> +	bool do_flush;
> +	bool do_sim;
> +};
> +
> +struct noisy_config *noisy_cfg[RTE_MAX_ETHPORTS];
> +
> +static inline void
> +do_write(char *vnf_mem)
> +{
> +	uint64_t i = rte_rand();
> +	uint64_t w = rte_rand();
> +
> +	vnf_mem[i % ((noisy_lkup_mem_sz * 1024 * 1024) /
> +			RTE_CACHE_LINE_SIZE)] = w;
> +}
> +
> +static inline void
> +do_read(char *vnf_mem)
> +{
> +	uint64_t i = rte_rand();
> +	uint64_t r;
> +
> +	r = vnf_mem[i % ((noisy_lkup_mem_sz * 1024 * 1024) /
> +			RTE_CACHE_LINE_SIZE)];
> +	r++;
> +}
> +
> +static inline void
> +do_readwrite(char *vnf_mem)
> +{
> +	do_read(vnf_mem);
> +	do_write(vnf_mem);
> +}
> +
> +/*
> + * Simulate route lookups as defined by commandline parameters
> + */
> +static void
> +sim_memory_lookups(struct noisy_config *ncf, uint16_t nb_pkts)
> +{
> +	uint16_t i, j;
> +
> +	if (!ncf->do_sim)
> +		return;
> +
> +	for (i = 0; i < nb_pkts; i++) {
> +		for (j = 0; j < noisy_lkup_num_writes; j++)
> +			do_write(ncf->vnf_mem);
> +		for (j = 0; j < noisy_lkup_num_reads; j++)
> +			do_read(ncf->vnf_mem);
> +		for (j = 0; j < noisy_lkup_num_reads_writes; j++)
> +			do_readwrite(ncf->vnf_mem);
> +	}
> +}
> +
> +static uint16_t
> +do_retry(uint16_t nb_rx, uint16_t nb_tx, struct rte_mbuf **pkts,
> +	 struct fwd_stream *fs)
> +{
> +	uint32_t retry = 0;
> +
> +	while (nb_tx < nb_rx && retry++ < burst_tx_retry_num) {
> +		rte_delay_us(burst_tx_delay_time);
> +		nb_tx += rte_eth_tx_burst(fs->tx_port, fs->tx_queue,
> +				&pkts[nb_tx], nb_rx - nb_tx);
> +	}
> +
> +	return nb_tx;
> +}
> +
> +static uint32_t
> +dropped_pkts(struct rte_mbuf **pkts, uint16_t nb_rx, uint16_t nb_tx)
> +{
> +	if (nb_tx < nb_rx) {
> +		do {
> +			rte_pktmbuf_free(pkts[nb_tx]);
> +		} while (++nb_tx < nb_rx);
> +	}
> +
> +	return nb_rx - nb_tx;
> +}
> +
> +/*
> + * Forwarding of packets in noisy VNF mode.  Forward packets but perform
> + * memory operations first as specified on cmdline.
> + *
> + * Depending on which commandline parameters are specified we have
> + * different cases to handle:
> + *
> + * 1. No FIFO size was given, so we don't do buffering of incoming
> + *    packets.  This case is pretty much what iofwd does but in this case
> + *    we also do simulation of memory accesses (depending on which
> + *    parameters were specified for it).
> + * 2. User wants do buffer packets in a FIFO and sent out overflowing
> + *    packets.
> + * 3. User wants a FIFO and specifies a time in ms to flush all packets
> + *    out of the FIFO

It reads like these are mutually exclusive, whereas I think they can be
combined too. Maybe you can just add a line about combinations or something.

> + */
> +static void
> +pkt_burst_noisy_vnf(struct fwd_stream *fs)
> +{
> +	const uint64_t freq_khz = rte_get_timer_hz() / 1000;
> +	struct noisy_config *ncf = noisy_cfg[fs->rx_port];
> +	struct rte_mbuf *pkts_burst[MAX_PKT_BURST];
> +	struct rte_mbuf *tmp_pkts[MAX_PKT_BURST];
> +	uint16_t nb_deqd = 0;
> +	uint16_t nb_rx = 0;
> +	uint16_t nb_tx = 0;
> +	uint16_t nb_enqd;
> +	unsigned int fifo_free;
> +	uint64_t delta_ms;
> +	bool needs_flush = false;
> +	uint64_t now;
> +
> +	nb_rx = rte_eth_rx_burst(fs->rx_port, fs->rx_queue,
> +			pkts_burst, nb_pkt_per_burst);
> +	if (unlikely(nb_rx == 0))

Perhaps you should jump down to 'if (ncf->do_flush)' to check if it's
time to flush some pkts regardless that you did not receive any new ones?

> +		return;
> +	fs->rx_packets += nb_rx;
> +
> +	if (!ncf->do_buffering) {
> +		sim_memory_lookups(ncf, nb_rx);
> +		nb_tx = rte_eth_tx_burst(fs->tx_port, fs->tx_queue,
> +				pkts_burst, nb_rx);
> +		if (unlikely(nb_tx < nb_rx) && fs->retry_enabled)
> +			nb_tx += do_retry(nb_rx, nb_tx, pkts_burst, fs);
> +		fs->tx_packets += nb_tx;
> +		fs->fwd_dropped += dropped_pkts(pkts_burst, nb_rx, nb_tx);
> +		return;
> +	}
> +
> +	fifo_free = rte_ring_free_count(ncf->f);
> +	if (fifo_free >= nb_rx) {
> +		nb_enqd = rte_ring_enqueue_burst(ncf->f,
> +				(void **) pkts_burst, nb_rx, NULL);
> +		if (nb_enqd < nb_rx)
> +			fs->fwd_dropped += (nb_rx - nb_enqd);

unlikely this would happen, but you'd need to free these pkts

> +		sim_memory_lookups(ncf, nb_rx);
> +	} else if (fifo_free < nb_rx) {

I don't think the if is needed, the else condition already gaurantees this

> +		nb_deqd = rte_ring_dequeue_burst(ncf->f,
> +				(void **) tmp_pkts, nb_rx, NULL);
> +		nb_enqd = rte_ring_enqueue_burst(ncf->f,
> +				(void **) pkts_burst, nb_deqd, NULL);
> +		if (nb_deqd > 0) {
> +			nb_tx = rte_eth_tx_burst(fs->tx_port,
> +					fs->tx_queue, tmp_pkts,
> +					nb_deqd);
> +			if (unlikely(nb_tx < nb_rx) && fs->retry_enabled)
> +				nb_tx += do_retry(nb_rx, nb_tx, tmp_pkts, fs);
> +			fs->fwd_dropped += dropped_pkts(tmp_pkts, nb_deqd,
> +							nb_tx);

Shouldn't there be sim_memory_lookups() for this path?

> +		}
> +	}
> +
> +	if (ncf->do_flush) {
> +		if (!ncf->prev_time)
> +			now = ncf->prev_time = rte_get_timer_cycles();
> +		else
> +			now = rte_get_timer_cycles();
> +		delta_ms = (now - ncf->prev_time) / freq_khz;
> +		needs_flush = delta_ms >= noisy_tx_sw_buf_flush_time &&
> +				noisy_tx_sw_buf_flush_time > 0 && !nb_tx;
> +	}
> +	while (needs_flush && !rte_ring_empty(ncf->f)) {
> +		unsigned int sent;
> +		nb_deqd = rte_ring_dequeue_burst(ncf->f, (void **)tmp_pkts,
> +				MAX_PKT_BURST, NULL);
> +		sent = rte_eth_tx_burst(fs->tx_port, fs->tx_queue,
> +					 tmp_pkts, nb_deqd);
> +		if (unlikely(sent < nb_deqd) && fs->retry_enabled)
> +			nb_tx += do_retry(nb_rx, nb_tx, tmp_pkts, fs);
> +		fs->fwd_dropped += dropped_pkts(tmp_pkts, nb_deqd, sent);
> +		ncf->prev_time = rte_get_timer_cycles();
> +	}
> +}
> +
> +#define NOISY_STRSIZE 256
> +#define NOISY_RING "noisy_ring_%d\n"
> +
> +static void
> +noisy_fwd_end(portid_t pi)
> +{
> +	rte_free(noisy_cfg[pi]);

this should be freed last

> +	rte_ring_free(noisy_cfg[pi]->f);
> +	rte_free(noisy_cfg[pi]->vnf_mem);
> +}
> +
> +static void
> +noisy_fwd_begin(portid_t pi)
> +{
> +	struct noisy_config *n;
> +	char name[NOISY_STRSIZE];
> +
> +	noisy_cfg[pi] = rte_zmalloc("testpmd noisy fifo and timers",
> +				nb_fwd_ports * sizeof(struct noisy_config),
> +				RTE_CACHE_LINE_SIZE);

I don't think 'nb_fwd_ports *' is needed. afaict, you'll just need one
struct per port.

> +	if (noisy_cfg == NULL) {
> +		rte_exit(EXIT_FAILURE,
> +				"rte_zmalloc(%d) struct noisy_config) failed\n",
> +				(int) nb_fwd_ports);
> +	}
> +	n = noisy_cfg[pi];
> +	snprintf(name, NOISY_STRSIZE, NOISY_RING, pi);
> +	n->f = rte_ring_create(name, noisy_tx_sw_bufsz,
> +			rte_socket_id(), 0);

Could be NULL

> +	if (noisy_lkup_mem_sz > 0) {
> +		n->vnf_mem = (char *) rte_zmalloc("vnf sim memory",
> +				 noisy_lkup_mem_sz * 1024 * 1024,
> +				 RTE_CACHE_LINE_SIZE);
> +		if (n->vnf_mem == NULL)
> +			rte_exit(EXIT_FAILURE,
> +				 "rte_zmalloc(%" PRIu64 ") for vnf memory) failed\n",
> +				 noisy_lkup_mem_sz);
> +	} else if (noisy_lkup_mem_sz == 0 && noisy_tx_sw_bufsz == 0) {
> +		rte_exit(EXIT_FAILURE,
> +			 "--noisy-tx-sw-buffer-size or --noisy-lkup-mem-size must be > 0\n");

s/mem-size/memory/

> +	}
> +	n->do_buffering = noisy_tx_sw_bufsz > 0;
> +	n->do_flush = noisy_tx_sw_buf_flush_time > 0;
> +	n->do_sim = noisy_lkup_num_writes + noisy_lkup_num_reads +
> +		    noisy_lkup_num_reads_writes;
> +}
> +
> +struct fwd_engine noisy_vnf_engine = {
> +	.fwd_mode_name  = "noisy",
> +	.port_fwd_begin = noisy_fwd_begin,
> +	.port_fwd_end   = noisy_fwd_end,
> +	.packet_fwd     = pkt_burst_noisy_vnf,
> +};
> +
> diff --git a/app/test-pmd/parameters.c b/app/test-pmd/parameters.c
> index 962fad7..85b44af 100644
> --- a/app/test-pmd/parameters.c
> +++ b/app/test-pmd/parameters.c
> @@ -625,6 +625,12 @@
>  		{ "vxlan-gpe-port",		1, 0, 0 },
>  		{ "mlockall",			0, 0, 0 },
>  		{ "no-mlockall",		0, 0, 0 },
> +		{ "noisy-tx-sw-buffer-size", 1, 0, 0 },
> +		{ "noisy-tx-sw-buffer-flushtime",        1, 0, 0 },
> +		{ "noisy-lkup-memory",     1, 0, 0 },
> +		{ "noisy-lkup-num-writes",         1, 0, 0 },
> +		{ "noisy-lkup-num-reads",          1, 0, 0 },
> +		{ "noisy-lkup-num-reads-writes",    1, 0, 0 },
>  		{ 0, 0, 0, 0 },
>  	};
>  
> @@ -1147,6 +1153,60 @@
>  				do_mlockall = 1;
>  			if (!strcmp(lgopts[opt_idx].name, "no-mlockall"))
>  				do_mlockall = 0;
> +			if (!strcmp(lgopts[opt_idx].name,
> +				    "noisy-tx-sw-buffer-size")) {
> +				n = atoi(optarg);
> +				if (n > 0)
> +					noisy_tx_sw_bufsz = n;
> +				else
> +					rte_exit(EXIT_FAILURE,
> +						"noisy-tx-sw-buffer-size must be > 0\n");

I commented in v4 about if this/others could be 'n >= 0' to allow for
setting to the default etc. No problem if you prefer not to allow it,
just not sure if comment is missed or not?

> +			}
> +			if (!strcmp(lgopts[opt_idx].name,
> +				    "noisy-tx-sw-buffer-flushtime")) {
> +				n = atoi(optarg);
> +				if (n >= 0)
> +					noisy_tx_sw_buf_flush_time = n;
> +				else
> +					rte_exit(EXIT_FAILURE,
> +						 "noisy-tx-sw-buffer-flushtime must be > 0\n");

log should match '>= 0'

> +			}
> +			if (!strcmp(lgopts[opt_idx].name,
> +				    "noisy-lkup-memory")) {
> +				n = atoi(optarg);
> +				if (n > 0)
> +					noisy_lkup_mem_sz = n;
> +				else
> +					rte_exit(EXIT_FAILURE,
> +						 "noisy-lkup-memory must be > 0\n");
> +			}
> +			if (!strcmp(lgopts[opt_idx].name,
> +				    "noisy-lkup-num-writes")) {
> +				n = atoi(optarg);
> +				if (n > 0)
> +					noisy_lkup_num_writes = n;
> +				else
> +					rte_exit(EXIT_FAILURE,
> +						 "noisy-lkup-num-writes must be > 0\n");
> +			}
> +			if (!strcmp(lgopts[opt_idx].name,
> +				    "noisy-lkup-num-reads")) {
> +				n = atoi(optarg);
> +				if (n > 0)
> +					noisy_lkup_num_reads = n;
> +				else
> +					rte_exit(EXIT_FAILURE,
> +						 "noisy-lkup-num-reads must be > 0\n");
> +			}
> +			if (!strcmp(lgopts[opt_idx].name,
> +				    "noisy-lkup-num-reads-writes")) {
> +				n = atoi(optarg);
> +				if (n > 0)
> +					noisy_lkup_num_reads_writes = n;
> +				else
> +					rte_exit(EXIT_FAILURE,
> +						 "noisy-lkup-num-reads-writes must be > 0\n");
> +			}
>  			break;
>  		case 'h':
>  			usage(argv[0]);
> diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
> index ee48db2..2b1b8c3 100644
> --- a/app/test-pmd/testpmd.c
> +++ b/app/test-pmd/testpmd.c
> @@ -157,6 +157,7 @@ struct fwd_engine * fwd_engines[] = {
>  	&tx_only_engine,
>  	&csum_fwd_engine,
>  	&icmp_echo_engine,
> +	&noisy_vnf_engine,
>  #if defined RTE_LIBRTE_PMD_SOFTNIC
>  	&softnic_fwd_engine,
>  #endif
> @@ -253,6 +254,40 @@ struct fwd_engine * fwd_engines[] = {
>  int16_t tx_rs_thresh = RTE_PMD_PARAM_UNSET;
>  
>  /*
> + * Configurable value of buffered packets before sending.
> + */
> +uint16_t noisy_tx_sw_bufsz;
> +
> +/*
> + * Configurable value of packet buffer timeout.
> + */
> +uint16_t noisy_tx_sw_buf_flush_time;
> +
> +/*
> + * Configurable value for size of VNF internal memory area
> + * used for simulating noisy neighbour behaviour
> + */
> +uint64_t noisy_lkup_mem_sz;
> +
> +/*
> + * Configurable value of number of random writes done in
> + * VNF simulation memory area.
> + */
> +uint64_t noisy_lkup_num_writes;
> +
> +/*
> + * Configurable value of number of random reads done in
> + * VNF simulation memory area.
> + */
> +uint64_t noisy_lkup_num_reads;
> +
> +/*
> + * Configurable value of number of random reads/wirtes done in

typo

> + * VNF simulation memory area.
> + */
> +uint64_t noisy_lkup_num_reads_writes;
> +
> +/*
>   * Receive Side Scaling (RSS) configuration.
>   */
>  uint64_t rss_hf = ETH_RSS_IP; /* RSS IP by default. */
> diff --git a/app/test-pmd/testpmd.h b/app/test-pmd/testpmd.h
> index a1f66147..796114f 100644
> --- a/app/test-pmd/testpmd.h
> +++ b/app/test-pmd/testpmd.h
> @@ -122,6 +122,8 @@ struct fwd_stream {
>  #endif
>  };
>  
> +
> +

Added whitespace

>  /** Descriptor for a single flow. */
>  struct port_flow {
>  	size_t size; /**< Allocated space including data[]. */
> @@ -243,6 +245,7 @@ struct fwd_engine {
>  extern struct fwd_engine tx_only_engine;
>  extern struct fwd_engine csum_fwd_engine;
>  extern struct fwd_engine icmp_echo_engine;
> +extern struct fwd_engine noisy_vnf_engine;
>  #ifdef SOFTNIC
>  extern struct fwd_engine softnic_fwd_engine;
>  #endif
> @@ -375,6 +378,13 @@ struct queue_stats_mappings {
>  extern int16_t tx_free_thresh;
>  extern int16_t tx_rs_thresh;
>  
> +extern uint16_t noisy_tx_sw_bufsz;
> +extern uint16_t noisy_tx_sw_buf_flush_time;
> +extern uint64_t noisy_lkup_mem_sz;
> +extern uint64_t noisy_lkup_num_writes;
> +extern uint64_t noisy_lkup_num_reads;
> +extern uint64_t noisy_lkup_num_reads_writes;
> +
>  extern uint8_t dcb_config;
>  extern uint8_t dcb_test;
>  
> diff --git a/doc/guides/testpmd_app_ug/run_app.rst b/doc/guides/testpmd_app_ug/run_app.rst
> index f301c2b..2bf4cf5 100644
> --- a/doc/guides/testpmd_app_ug/run_app.rst
> +++ b/doc/guides/testpmd_app_ug/run_app.rst
> @@ -340,6 +340,7 @@ The commandline options are:
>         icmpecho
>         ieee1588
>         tm
> +       noisy
>  
>  *   ``--rss-ip``
>  
> @@ -498,3 +499,35 @@ The commandline options are:
>  *   ``--no-mlockall``
>  
>      Disable locking all memory.
> +
> +*   ``--noisy-tx-sw-buffer-size``
> +
> +    Set the number of maximum elements  of the FIFO queue to be created
> +    for buffering packets. Only available with the noisy forwarding mode.
> +    The default value is 0.
> +
> +*   ``--noisy-tx-sw-buffer-flushtime``
> +
> +    Set the time before packets in the FIFO queue is flushed.
> +    Only available with the noisy forwarding mode. The default value is 0.
> +
> +*   ``--noisy-lkup-memory=N``
> +

Not sure about the convention of using N. Other descriptions seem to
reference it explicitly.

> +    Set the size of the noisy neighbour simulation memory buffer in MB.
> +    Only available with the noisy forwarding mode. The default value is 0.
> +
> +
> +*   ``--noisy-lkup-num-reads=N``
> +
> +    Set the number of reads to be done in noisy neighbour simulation memory buffer.
> +    Only available with the noisy forwarding mode. The default value is 0.
> +
> +*   ``--noisy-lkup-num-writes=N``
> +
> +    Set the number of writes to be done in noisy neighbour simulation memory buffer.
> +    Only available with the noisy forwarding mode. The default value is 0.
> +
> +*   ``--noisy-lkup-num-reads-writes=N``
> +
> +    Set the number of r/w accesses to be done in noisy neighbour simulation memory buffer.
> +    Only available with the noisy forwarding mode. The default value is 0.
> diff --git a/doc/guides/testpmd_app_ug/testpmd_funcs.rst b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
> index dde205a..e2f9db2 100644
> --- a/doc/guides/testpmd_app_ug/testpmd_funcs.rst
> +++ b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
> @@ -289,7 +289,7 @@ set fwd
>  Set the packet forwarding mode::
>  
>     testpmd> set fwd (io|mac|macswap|flowgen| \
> -                     rxonly|txonly|csum|icmpecho) (""|retry)
> +                     rxonly|txonly|csum|icmpecho|noisy) (""|retry)
>  
>  ``retry`` can be specified for forwarding engines except ``rx_only``.
>  
> @@ -323,8 +323,11 @@ The available information categories are:
>  * ``softnic``: Demonstrates the softnic forwarding operation. In this mode, packet forwarding is
>    similar to I/O mode except for the fact that packets are loopback to the softnic ports only. Therefore, portmask parameter should be set to softnic port only. The various software based custom NIC pipelines specified through the softnic firmware (DPDK packet framework script) can be tested in this mode. Furthermore, it allows to build 5-level hierarchical QoS scheduler as a default option that can be enabled through CLI once testpmd application is initialised. The user can modify the default scheduler hierarchy or can specify the new QoS Scheduler hierarchy through CLI. Requires ``CONFIG_RTE_LIBRTE_PMD_SOFTNIC=y``.
>  
> -Example::
> +* ``noisy``: Noisy neighbour simulation.
> +  Simulate more realistic behavior of a guest machine engaged in receiving
> +  and sending packets performing Virtual Network Function (VNF).
>  
> +Example::
>     testpmd> set fwd rxonly
>  
>     Set rxonly packet forwarding mode
> 

There's a 'new blank line at EOF warning' here when applying