Re: [dpdk-stable] [dpdk-dev] [PATCH] app/testpmd: fix segment number check

[Slava Ovsiienko <viacheslavo@nvidia.com>]

Hi, Andrew

Thank you for the review, please, see below.

> -----Original Message-----
> From: Andrew Boyer <aboyer@pensando.io>
> Sent: Friday, December 11, 2020 18:00
> To: Slava Ovsiienko <viacheslavo@nvidia.com>
> Cc: dev@dpdk.org; NBU-Contact-Thomas Monjalon <thomas@monjalon.net>;
> ferruh.yigit@intel.com; stable@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] app/testpmd: fix segment number check
> 
> 
> 
> > On Dec 11, 2020, at 10:07 AM, Viacheslav Ovsiienko
> <viacheslavo@nvidia.com> wrote:
> >
> > The --txpkts command line parameter was silently ignored due to
> > application was unable to check the Tx queue ring sizes for non
> > configured ports [1].
> 
> ... ignored because the application...
OK, will fix.

> 
> > The "set txpkts <len0[,len1]*>" was also rejected if there was some
> > stopped or /unconfigured port.
> 
> ... was a stopped or unconfigured ...
OK, will fix.

> 
> >
> > This provides the following:
> >
> >  - number of segment check is performed against
> >    configured Tx queues only
> >
> >  - the capability to send single packet is supposed to
> >    be very basic and always supported, the setting segment
> >    number to 1 is always allowed, no check performed
> >
> >  - at the moment of Tx queue setup the descriptor number is
> >    checked against configured segment number
> >
> > Fixes: 8dae835d88b7 ("app/testpmd: remove restriction on Tx segments
> > set")
> > Cc: stable@dpdk.org
> > Bugzilla ID: 584
> >
> > Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
> > ---
> > app/test-pmd/cmdline.c |  5 +++++
> > app/test-pmd/config.c  | 21 ++++++++++++++++-----
> > app/test-pmd/testpmd.c |  7 ++++++-
> > 3 files changed, 27 insertions(+), 6 deletions(-)
> >
> > diff --git a/app/test-pmd/cmdline.c b/app/test-pmd/cmdline.c index
> > 0d2d6aa..86388a2 100644
> > --- a/app/test-pmd/cmdline.c
> > +++ b/app/test-pmd/cmdline.c
> > @@ -2798,6 +2798,11 @@ struct cmd_setup_rxtx_queue {
> > 		if (!numa_support || socket_id == NUMA_NO_CONFIG)
> > 			socket_id = port->socket_id;
> >
> > +		if (port->nb_tx_desc[res->qid] < tx_pkt_nb_segs) {
> > +			printf("Failed to setup TX queue: "
> 
> setup -> set up
Disagree, it is quite common in testpmd code to use "setup" wording,
 I just copy-pasted the message from the neighbor lines.

> I find it helpful when the numbers are logged in the error message.  Like
> “nb_desc 8 < nb_segs 16”.
> 
> > +			       "not enough descriptors\n");
> > +			return;
> > +		}
> 
Do you think it is worth to be informative so much? OK, will add.

> Why is there a relationship between the number of descriptors and the
> number of segments? For our device, there isn’t. We can send 16 Tx segments
> per descriptor and (I suppose) you could try to create an 8 descriptor ring.
> 
> Maybe this is to protect a simpler device that consumes one descriptor per
> segment? If so, the check would ideally be conditioned on a related device
> capability flag. I’m not sure if there is such a flag today.
There is no correlation between  n_desc and n_seg for Tx in mlx5 PMD either.
And there is no information provided how many descriptors should be
provided for the multi-segment packets.

If we have a look at original commit being fixed
("app/testpmd: remove restriction on Tx segments set") we'll see:

-       if (nb_segs >= (unsigned) nb_txd) {
-               printf("nb segments per TX packets=%u >= nb_txd=%u - ignored\n",
-                      nb_segs, (unsigned int) nb_txd);

So, the check was added in replacement for other, more strict, check.
Now we are just improving one a little bit.


> 
> > 		ret = rte_eth_tx_queue_setup(res->portid,
> > 					     res->qid,
> > 					     port->nb_tx_desc[res->qid],
> > diff --git a/app/test-pmd/config.c b/app/test-pmd/config.c index
> > b51de59..a6fccfa 100644
> > --- a/app/test-pmd/config.c
> > +++ b/app/test-pmd/config.c
> > @@ -3911,12 +3911,18 @@ struct igb_ring_desc_16_bytes {
> > 		for (queue_id = 0; queue_id < nb_txq; queue_id++) {
> > 			ret = get_tx_ring_size(port_id, queue_id, &ring_size);
> >
> > -			if (ret)
> > +			/* Do the check only for the active/configured ports.
> */
> > +			if (ret == -EINVAL)
> > +				continue;
> > +			if (ret) {
> > +				printf("failed to get ring size for TX "
> > +				       "queue(%u) Port(%u) - txpkts ignored\n",
> > +				       port_id, queue_id);
> > 				return true;
> > -
> > +			}
> > 			if (ring_size < nb_segs) {
> > -				printf("nb segments per TX packets=%u >= "
> > -				       "TX queue(%u) ring_size=%u - ignored\n",
> > +				printf("nb segments per TX packets=%u >= TX
> "
> > +				       "queue(%u) ring_size=%u - txpkts
> ignored\n",
> > 				       nb_segs, queue_id, ring_size);
> > 				return true;
> > 			}
> > @@ -3932,7 +3938,12 @@ struct igb_ring_desc_16_bytes {
> > 	uint16_t tx_pkt_len;
> > 	unsigned int i;
> >
> > -	if (nb_segs_is_invalid(nb_segs))
> > +	/*
> > +	 * For single sengment settings failed check is ignored.
> > +	 * It is a very basic capability to send the single segment
> > +	 * packets, suppose it is always supported.
> 
> sengment -> segment
> ... to send single segment...
> suppose -> assume
OK, np, will fix.

> 
> > +	 */
> > +	if (nb_segs > 1 && nb_segs_is_invalid(nb_segs))
> > 		return;
> >
> > 	/*
> > diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c index
> > 33fc0fd..9ea0145 100644
> > --- a/app/test-pmd/testpmd.c
> > +++ b/app/test-pmd/testpmd.c
> > @@ -2575,6 +2575,11 @@ struct extmem_param {
> > 			port->need_reconfig_queues = 0;
> > 			/* setup tx queues */
> > 			for (qi = 0; qi < nb_txq; qi++) {
> > +				if (port->nb_tx_desc[qi] < tx_pkt_nb_segs) {
> > +					printf("Failed to setup TX queue: "
> > +					       "not enough descriptors\n");
> 
> Same comments as above
OK.

> 
> > +					goto fail;
> > +				}
> > 				if ((numa_support) &&
> > 					(txring_numa[pi] !=
> NUMA_NO_CONFIG))
> > 					diag = rte_eth_tx_queue_setup(pi, qi,
> @@ -2589,7 +2594,7 @@
> > struct extmem_param {
> >
> > 				if (diag == 0)
> > 					continue;
> > -
> > +fail:
> > 				/* Fail to setup tx queue, return */
> > 				if (rte_atomic16_cmpset(&(port-
> >port_status),
> >
> 	RTE_PORT_HANDLING,
> > --
> > 1.8.3.1
> >

Thanks a lot, I will wait for a while for more comments and provide v2.

With best regards, Slava