[dpdk-dev] [PATCH] examples/ip_fragmentation: support bigger packets

Ananyev, Konstantin konstantin.ananyev at intel.com
Thu Dec 20 13:11:21 CET 2018



> 
> Hi,
> In some vendores (like Mellanox, that reflects the linux behavior in this case) the Rx and Tx configurations must be the same, therefore it is
> not enough to configure the max_rx_pkt_len to JUMBO_FRAME_MAX_SIZE, we also need to configure the MTU size in order to receive
> large packets.

Interesting, didn't know that.
Does it mean that l3fwd and bunch of other sample apps that use max_rx_pkt_len to setup MTU,
don't work properly with mlx devices (not able to run with jumbo-frame enabled)?

> In order to avoid from adding another configuration to the command line, we can configure the MTU to be equal to  max_rx_pkt_len, and it
> won't change the functionality of the test.

I don't have any objections with new option for MTU size (-m) if you need it.
It was just unclear to me why it was necessary for you.
But yes, setting MTU to the correlated with max_rx_ptk_len value sounds like a good idea.

> 
> In addition there are PMDs that need to enable the scatter-gather so it will be functional for RX frames bigger then mbuf size. We can add
> the configuration and avoid changing the mbuf size.

You mean check if MTU is bigger than mbuf size, and if so setup (DEV_RX_OFFLOAD_JUMBO_FRAME | DEV_RX_OFFLOAD_SCATTER)
?
Konstantin


> 
> What do you think about this solution?
> 
> Thanks,
> Noa.
> 
> -----Original Message-----
> From: Ananyev, Konstantin [mailto:konstantin.ananyev at intel.com]
> Sent: Thursday, December 20, 2018 2:18 AM
> To: Noa Ezra <noae at mellanox.com>
> Cc: dev at dpdk.org
> Subject: RE: [PATCH] examples/ip_fragmentation: support bigger packets
> 
> Hi,
> 
> >
> > Adding MTU and mbuf size configuration to the application's command
> > line, in order to be able to receive all packet sizes by the NIC and
> > DPDK application.
> > The maximum transmission unit (MTU) is the largest size packet in
> > bytes that can be sent on the network, therefore before adding MTU
> > parameter, the NIC could not receive packets larger than 1500 bytes,
> > which is the default MTU size.
> 
> I wonder why is that?
> Currently ip_fragmentation sets max_rx_pkt_len to up to 9.5KB:
> 
> static struct rte_eth_conf port_conf = {
>         .rxmode = {
>                 .max_rx_pkt_len = JUMBO_FRAME_MAX_SIZE, ...
> 
> local_port_conf.rxmode.max_rx_pkt_len = RTE_MIN(
>                     dev_info.max_rx_pktlen,
>                     local_port_conf.rxmode.max_rx_pkt_len);
> 
> That in theory should be enough to enable jumbo frame RX.
> Did you find it is not working as expected, if yes on which NIC?
> 
> > The mbuf is the memory buffer that contains the packet. Before adding
> > mbuf parameter, the DPDK application could not receive packets larger
> > than 2KB, which is the default mbuf size.
> 
> Again why is that?
> All packets that do support scatter-gather RX should be able to RX frames bigger then mbuf size (if properly configured of course).
> Are you trying to make it work on NICs with no multi-segment support for RX/TX?
> But then how you plan to do TX (usually it is symmetric for RX/TX)?
> 
> >
> > Signed-off-by: Noa Ezra <noae at mellanox.com>
> > ---
> >  doc/guides/sample_app_ug/ip_frag.rst | 18 ++++++++-
> >  examples/ip_fragmentation/main.c     | 77 +++++++++++++++++++++++++++++++++---
> >  2 files changed, 88 insertions(+), 7 deletions(-)
> >
> > diff --git a/doc/guides/sample_app_ug/ip_frag.rst
> > b/doc/guides/sample_app_ug/ip_frag.rst
> > index 7914a97..13933c7 100644
> > --- a/doc/guides/sample_app_ug/ip_frag.rst
> > +++ b/doc/guides/sample_app_ug/ip_frag.rst
> > @@ -53,7 +53,7 @@ Application usage:
> >
> >  .. code-block:: console
> >
> > -    ./build/ip_fragmentation [EAL options] -- -p PORTMASK [-q NQ]
> > +    ./build/ip_fragmentation [EAL options] -- -p PORTMASK [-q NQ] [-b
> > + MBUFSIZE] [-m MTUSIZE]
> >
> >  where:
> >
> > @@ -61,6 +61,15 @@ where:
> >
> >  *   -q NQ is the number of queue (=ports) per lcore (the default is 1)
> >
> > +*   -b MBUFSIZE is the mbuf size in bytes (the default is 2048)
> > +
> > +*   -m MTUSIZE is the mtu size in bytes (the default is 1500)
> > +
> > +The MTU is the maximum size of a single data unit that can be
> > +transmitted over the network, therefore it must be greater than the requested max packet size, otherwise the NIC won't be able to get
> the packet.
> > +The mbuf is a buffer that is used by the DPDK application to store
> > +message buffers.If not using scatter then the mbuf size must be
> > +greater than the requested max packet size, otherwise the DPDK will not be able to receive the packet.
> >  To run the example in linuxapp environment with 2 lcores (2,4) over 2 ports(0,2) with 1 RX queue per lcore:
> >
> >  .. code-block:: console
> > @@ -96,6 +105,13 @@ To run the example in linuxapp environment with 1
> > lcore (4) over 2 ports(0,2) wi
> >
> >      ./build/ip_fragmentation -l 4 -n 3 -- -p 5 -q 2
> >
> > +To run the example with defined MTU size 4000 bytes and mbuf size 9000 byes:
> > +
> > +.. code-block:: console
> > +
> > +    ./build/ip_fragmentation -l 4 -n 3 -- -p 5 -m 4000 -b 9000
> > +
> > +
> >  To test the application, flows should be set up in the flow generator
> > that match the values in the  l3fwd_ipv4_route_array and/or l3fwd_ipv6_route_array table.
> >
> > diff --git a/examples/ip_fragmentation/main.c
> > b/examples/ip_fragmentation/main.c
> > index 17a877d..0cf23b4 100644
> > --- a/examples/ip_fragmentation/main.c
> > +++ b/examples/ip_fragmentation/main.c
> > @@ -111,6 +111,10 @@
> >
> >  static int rx_queue_per_lcore = 1;
> >
> > +static int mbuf_size = RTE_MBUF_DEFAULT_BUF_SIZE;
> > +
> > +static int mtu_size = ETHER_MTU;
> > +
> >  #define MBUF_TABLE_SIZE  (2 * MAX(MAX_PKT_BURST, MAX_PACKET_FRAG))
> >
> >  struct mbuf_table {
> > @@ -425,7 +429,6 @@ struct rte_lpm6_config lpm6_config = {
> >  		 * Read packet from RX queues
> >  		 */
> >  		for (i = 0; i < qconf->n_rx_queue; i++) {
> > -
> >  			portid = qconf->rx_queue_list[i].portid;
> >  			nb_rx = rte_eth_rx_burst(portid, 0, pkts_burst,
> >  						 MAX_PKT_BURST);
> > @@ -455,9 +458,11 @@ struct rte_lpm6_config lpm6_config = {  static
> > void  print_usage(const char *prgname)  {
> > -	printf("%s [EAL options] -- -p PORTMASK [-q NQ]\n"
> > +	printf("%s [EAL options] -- -p PORTMASK [-q NQ] [-b MBUFSIZE] [-m MTUSIZE]\n"
> >  	       "  -p PORTMASK: hexadecimal bitmask of ports to configure\n"
> > -	       "  -q NQ: number of queue (=ports) per lcore (default is 1)\n",
> > +	       "  -q NQ: number of queue (=ports) per lcore (default is 1)\n"
> > +	       "  -b MBUFSIZE: set the data size of mbuf\n"
> > +	       "  -m MTUSIZE: set the MTU size\n",
> >  	       prgname);
> >  }
> >
> > @@ -496,6 +501,38 @@ struct rte_lpm6_config lpm6_config = {
> >  	return n;
> >  }
> >
> > +static int
> > +parse_mbufsize(const char *q_arg)
> > +{
> > +	char *end = NULL;
> > +	unsigned long mbuf;
> > +
> > +	/* parse hexadecimal string */
> 
> You expect decimal string below.
> 
> > +	mbuf = strtoul(q_arg, &end, 10);
> > +	if ((q_arg[0] == '\0') || (end == NULL) || (*end != '\0'))
> > +		return -1;
> 
> You probably need to set and test errno too.
> 
> > +	if (mbuf == 0)
> > +		return -1;
> > +
> > +	return mbuf;
> > +}
> 
> 
> These 2 parse functions looks identical.
> Why you need two of them?
> 
> > +
> > +static int
> > +parse_mtusize(const char *q_arg)
> > +{
> > +	char *end = NULL;
> > +	unsigned long mtu;
> > +
> > +	/* parse hexadecimal string */
> > +	mtu = strtoul(q_arg, &end, 10);
> > +	if ((q_arg[0] == '\0') || (end == NULL) || (*end != '\0'))
> > +		return -1;
> > +	if (mtu == 0)
> > +		return -1;
> > +
> > +	return mtu;
> > +}
> > +
> >  /* Parse the argument given in the command line of the application */
> > static int  parse_args(int argc, char **argv) @@ -510,7 +547,7 @@
> > struct rte_lpm6_config lpm6_config = {
> >
> >  	argvopt = argv;
> >
> > -	while ((opt = getopt_long(argc, argvopt, "p:q:",
> > +	while ((opt = getopt_long(argc, argvopt, "p:q:b:m:",
> >  				  lgopts, &option_index)) != EOF) {
> >
> >  		switch (opt) {
> > @@ -534,6 +571,26 @@ struct rte_lpm6_config lpm6_config = {
> >  			}
> >  			break;
> >
> > +		/* mbufsize */
> > +		case 'b':
> > +			mbuf_size = parse_mbufsize(optarg);
> > +			if (mbuf_size < 0) {
> > +				printf("invalid mbuf size\n");
> > +				print_usage(prgname);
> > +				return -1;
> > +			}
> > +			break;
> > +
> > +		/* mtusize */
> > +		case 'm':
> > +			mtu_size = parse_mtusize(optarg);
> > +			if (mtu_size < 0) {
> > +				printf("invalid mtu size\n");
> > +				print_usage(prgname);
> > +				return -1;
> > +			}
> > +			break;
> > +
> >  		/* long options */
> >  		case 0:
> >  			print_usage(prgname);
> > @@ -777,9 +834,8 @@ struct rte_lpm6_config lpm6_config = {
> >  			RTE_LOG(INFO, IP_FRAG, "Creating direct mempool on socket %i\n",
> >  					socket);
> >  			snprintf(buf, sizeof(buf), "pool_direct_%i", socket);
> > -
> >  			mp = rte_pktmbuf_pool_create(buf, NB_MBUF, 32,
> > -				0, RTE_MBUF_DEFAULT_BUF_SIZE, socket);
> > +				0, mbuf_size, socket);
> >  			if (mp == NULL) {
> >  				RTE_LOG(ERR, IP_FRAG, "Cannot create direct mempool\n");
> >  				return -1;
> > @@ -892,6 +948,15 @@ struct rte_lpm6_config lpm6_config = {
> >  		    dev_info.max_rx_pktlen,
> >  		    local_port_conf.rxmode.max_rx_pkt_len);
> >
> > +		/* set the mtu to the maximum received packet size */
> > +		ret = rte_eth_dev_set_mtu(portid, mtu_size);
> > +		if (ret < 0) {
> > +			printf("\n");
> > +			rte_exit(EXIT_FAILURE, "Set MTU failed: "
> > +				"err=%d, port=%d\n",
> > +			ret, portid);
> > +		}
> > +
> >  		/* get the lcore_id for this port */
> >  		while (rte_lcore_is_enabled(rx_lcore_id) == 0 ||
> >  		       qconf->n_rx_queue == (unsigned)rx_queue_per_lcore) {
> > --
> > 1.8.3.1



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