RE: [EXT] Re: [dpdk-stable] [PATCH v2] test: avoid hang if queues are full and Tx fails

[Rakesh Kudurumalla <rkudurumalla@marvell.com>]

> -----Original Message-----
> From: Thomas Monjalon <thomas@monjalon.net>
> Sent: Monday, November 22, 2021 2:28 PM
> To: Rakesh Kudurumalla <rkudurumalla@marvell.com>
> Cc: stable@dpdk.org; dev@dpdk.org; david.marchand@redhat.com;
> ferruh.yigit@intel.com; andrew.rybchenko@oktetlabs.ru;
> ajit.khaparde@broadcom.com; Jerin Jacob Kollanukkaran
> <jerinj@marvell.com>
> Subject: Re: [EXT] Re: [dpdk-stable] [PATCH v2] test: avoid hang if queues are
> full and Tx fails
> 
> 22/11/2021 08:59, Rakesh Kudurumalla:
> > From: Thomas Monjalon <thomas@monjalon.net>
> > > 20/07/2021 18:50, Rakesh Kudurumalla:
> > > > Current pmd_perf_autotest() in continuous mode tries to enqueue
> > > > MAX_TRAFFIC_BURST completely before starting the test. Some
> > > > drivers cannot accept complete MAX_TRAFFIC_BURST even though
> rx+tx
> > > > desc
> > > count
> > > > can fit it.
> > >
> > > Which driver is failing to do so?
> > > Why it cannot enqueue 32 packets?
> >
> > Octeontx2 driver is failing to enqueue because hardware buffers are full
> before test.
> 
> Why hardware buffers are full?
Hardware buffers are full because number of number of descriptors in continuous mode 
Is less than MAX_TRAFFIC_BURST, so if enque fails , there is no way hardware can drop the
Packets . pmd_per_autotest application evaluates performance after enqueueing packets
Initially.
> 
> > pmd_perf_autotest() in continuous mode tries to enqueue
> > MAX_TRAFFIC_BURST (2048) before starting the test.
> >
> > > > This patch changes behaviour to stop enqueuing after few retries.
> > >
> > > If there is a real limitation, there will be issues in more places
> > > than this test program.
> > > I feel it should be addressed either in the driver or at ethdev level.
> > >
> > > [...]
> > > > @@ -480,10 +483,19 @@ main_loop(__rte_unused void *args)
> > > >  			nb_tx = RTE_MIN(MAX_PKT_BURST, num);
> > > >  			nb_tx = rte_eth_tx_burst(portid, 0,
> > > >  						&tx_burst[idx], nb_tx);
> > > > +			if (nb_tx == 0)
> > > > +				retry_cnt++;
> > > >  			num -= nb_tx;
> > > >  			idx += nb_tx;
> > > > +			if (retry_cnt == MAX_RETRY_COUNT) {
> > > > +				retry_cnt = 0;
> > > > +				break;
> > > > +			}
> 
>