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

[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?