[dpdk-dev] [PATCH] ethdev: check number of queues less than RTE_ETHDEV_QUEUE_STAT_CNTRS

[Alejandro Lucero]

On Thu, Nov 10, 2016 at 4:01 PM, Thomas Monjalon <thomas.monjalon at 6wind.com>
wrote:

> 2016-11-10 15:43, Alejandro Lucero:
> > On Thu, Nov 10, 2016 at 2:42 PM, Thomas Monjalon <
> thomas.monjalon at 6wind.com>
> > wrote:
> >
> > > 2016-11-10 14:00, Alejandro Lucero:
> > > > From: Bert van Leeuwen <bert.vanleeuwen at netronome.com>
> > > >
> > > > A device can have more than RTE_ETHDEV_QUEUE_STAT_CNTRS queues which
> > > > is used inside struct rte_eth_stats. Ideally, DPDK should be built
> with
> > > > RTE_ETHDEV_QUEUE_STAT_CNTRS to the maximum number of queues a device
> > > > can support, 65536, as uint16_t is used for keeping those values for
> > > > RX and TX. But of course, having such big arrays inside struct
> > > rte_eth_stats
> > > > is not a good idea.
> > >
> > > RTE_ETHDEV_QUEUE_STAT_CNTRS come from a limitation in Intel devices.
> > > They have limited number of registers to store the stats per queue.
> > >
> > > > Current default value is 16, which could likely be changed to 32 or
> 64
> > > > without too much opposition. And maybe it would be a good idea to
> modify
> > > > struct rte_eth_stats for allowing dynamically allocated arrays and
> maybe
> > > > some extra fields for keeping the array sizes.
> > >
> > > Yes
> > > and? what is your issue exactly? with which device?
> > > Please explain the idea brought by your patch.
> > >
> >
> > Netronome NFP devices support 128 queues and future version will support
> > 1024.
> >
> > A particular VF, our PMD just supports VFs, could get as much as 128.
> > Although that is not likely, that could be an option for some client.
> >
> > Clients want to use a DPDK coming with a distribution, so changing the
> > RTE_ETHDEV_QUEUE_STAT_CNTRS depending on the present devices is not an
> > option.
> >
> > We would be happy if RTE_ETHDEV_QUEUE_STAT_CNTRS could be set to 1024,
> > covering current and future requirements for our cards, but maybe having
> > such big arrays inside struct rte_eth_stats is something people do not
> want
> > to have.
> >
> > A solution could be to create such arrays dynamically based on the device
> > to get the stats from. For example, call to rte_eth_dev_configure could
> > have ax extra field for allocating a rte_eth_stats struct, which will be
> > based on nb_rx_q and nb_tx_q params already given to that function.
> >
> > Maybe the first thing to know is what people think about just
> incrementing
> > RTE_ETHDEV_QUEUE_STAT_CNTRS to 1024.
> >
> > So Thomas, what do you think about this?
>
> I think this patch is doing something else :)
>
>
Sure. But the problem the patch solves is pointing to this, IMHO, bigger
issue.


> I'm not sure what is better between big arrays and variable size.
> I think you must explain these 2 options in another thread,
> because I'm not sure you will have enough attention in a thread starting
> with
> "check number of queues less than RTE_ETHDEV_QUEUE_STAT_CNTRS".
>

Agree. I'll do that then.

Thanks