Re: reuse the packets after tx burst

[Lokesh Chakka <lvenkatakumarchakka@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 5360 bytes --]

Please ignore the type.
It Solved *OUR* problem.


Thanks & Regards
--
Lokesh Chakka.


On Thu, Aug 15, 2024 at 9:48 PM Lokesh Chakka <lvenkatakumarchakka@gmail.com>
wrote:

> Hi Stephen,
>
> Thank you for the information.
> It solved your problem.
>
> Regards.
> Lokesh.
>
>
> On Wed, 14 Aug, 2024, 20:29 Stephen Hemminger, <stephen@networkplumber.org>
> wrote:
>
>> On Wed, 14 Aug 2024 17:57:40 +0530
>> Lokesh Chakka <lvenkatakumarchakka@gmail.com> wrote:
>>
>> > hi stephen,
>> >
>> > Thanks for your response. However it seems the solution is not working.
>> The
>> > following is the modified snippet....
>> >
>> > while( condition )
>> > {
>> >      for( pkt_count=0; pkt_count<num_of_pkts_per_queue; pkt_count++ )
>> >      {
>> >           rte_mbuf_refcnt_set( mbuf[pkt_count], 2 );// setting to two -
>> > first and second iteration
>> >      }
>> >      for( pkt_count=0; pkt_count<5; pkt_count++ )
>> >      {
>> >           fprintf( stderr, "%s %d %u\n", __func__, __LINE__,
>> > rte_mbuf_refcnt_read( mbuf[pkt_count] ) );//able to print two- first and
>> > second iteration
>> >      }
>> >      if( rte_eth_tx_burst( port_id, 0, mbuf, num_of_pkts_per_queue ) !=
>> > num_of_pkts_per_queue )
>> >      {
>> >           fprintf( stderr, "%s %d %d %s\n", __func__, __LINE__,
>> rte_errno,
>> > rte_strerror(rte_errno) );//failing second time
>> >           rte_exit( EXIT_FAILURE, "%s %d rte_eth_tx_burst port id:
>> %u\n",
>> > __func__, __LINE__, port_id );
>> >      }
>> >      fprintf( stderr, "%s %d port: %u sent %u packets\n", __func__,
>> > __LINE__, port_id, num_of_pkts_per_queue );//able to send once - first
>> > iteration only
>> >      for( pkt_count=0; pkt_count<5; pkt_count++ )
>> >      {
>> >           fprintf( stderr, "%s %d %u\n", __func__, __LINE__,
>> > rte_mbuf_refcnt_read( mbuf[pkt_count] ) );//refcnt is printing one
>> >      }
>> > }
>> >
>> > There seems to be some more gap in my understanding. Could you please
>> help
>> > understand the issue?
>> >
>> > Thanks & Regards
>> > --
>> > Lokesh Chakka.
>> >
>> >
>> > On Mon, Aug 12, 2024 at 8:22 PM Stephen Hemminger <
>> > stephen@networkplumber.org> wrote:
>> >
>> > > On Mon, 12 Aug 2024 15:55:50 +0530
>> > > Lokesh Chakka <lvenkatakumarchakka@gmail.com> wrote:
>> > >
>> > > > hello,
>> > > >
>> > > > Here is a small piece of code :
>> > > >
>> > > > while( condition )
>> > > > {
>> > > >
>> > > >       if( rte_eth_tx_burst( port_id, 0, mbuf, num_of_pkts_per_queue
>> ) !=
>> > > > num_of_pkts_per_queue )
>> > > >       {
>> > > >               fprintf( stderr, "%d %s\n", rte_errno,
>> > > rte_strerror(rte_errno) );
>> > > >               rte_exit( EXIT_FAILURE, "%s %d rte_eth_tx_burst port
>> id:
>> > > %u\n",
>> > > > __func__, __LINE__, port_id );//second iteration failing.
>> > > >       }
>> > > >       fprintf( stderr, "%s %d port: %u packet: %c sent %u
>> packets\n",
>> > > > __func__, __LINE__, port_id, argv[3][0], num_of_pkts_per_queue
>> > > > );//printing once
>> > > >       for( pkt_count=0; pkt_count<num_of_pkts_per_queue;
>> pkt_count++ )
>> > > >       {//want to send same data again...!!!
>> > > >               mbuf[pkt_count]->pkt_len = mbuf[pkt_count]->data_len
>> =
>> > > dev_info.max_mtu;
>> > > >
>> > > >       }
>> > > >
>> > > > }
>> > > >
>> > > > Can someone help me understand how to reuse the packets again to
>> send the
>> > > > same data ?
>> > > >
>> > >
>> > > When packet is passed to tx_burst, the ownership of that mbuf is
>> passed
>> > > to the driver. The driver will free it after it is sent.
>> > >
>> > > One option would be to increase the reference count on the packet
>> before
>> > > sending.
>> > > Using rte_mbuf_refcnt_update() function to add one to refcount.
>> > > Then the driver will decrement refcount and the refcount will still
>> be one
>> > > (not freed).
>> > >
>> > > Assume this is some kind of packet generator.
>> > >
>>
>>
>> Don't use refcnt_set(), you want to add an additional refcount not force
>> it to two.
>> The device driver may hold onto the mbuf for a while after it was passed
>> to tx_burst
>> so can't assume a value of two.
>>
>> If the number actually queued is less that the number requested, that
>> means the device
>> transmit queue is now full. Need to handle that case.
>>
>> Something like this might get you started:
>>
>>
>> volatile running = true;
>>
>> void flood(uint16_t port_id, struct rte_mbufs *mbufs[], uint16_t num_pkts)
>> {
>>
>>         while (running) {
>>                 /* Add additional reference to retain the packets */
>>                 for (uint16_t i = 0; i < num_pkts; i++)
>>                         rte_mbuf_refcnt_update(mbufs[i], 1);
>>
>>                 uint16_t sent = rte_eth_tx_burst(port_id, queue_id,
>> mbufs, num_pkts);
>>
>>                 if (sent < num_pkts) {
>>                         /* device transmit queue was full, drop our
>> reference */
>>                         for (uint16_t i = sent; i < num_pkts; i++)
>>                                 rte_pktmbuf_free(mbufs[i]);
>>                 }
>>         }
>>
>>         /* Don't leak original version */
>>         rte_pktmbuf_free_bulk(mbufs, num_pkts);
>>
>> }
>>
>>
>>

[-- Attachment #2: Type: text/html, Size: 7578 bytes --]