Re: [dpdk-dev] [dpdk-techboard] [PATCH V5 1/2] dpdk: resolve compiling errors for per-queue stats

[Thomas Monjalon <thomas@monjalon.net>]

28/09/2020 10:59, Ferruh Yigit:
> On 9/27/2020 4:16 AM, Min Hu (Connor) wrote:
> > From: Huisong Li <lihuisong@huawei.com>
> > 
> > Currently, only statistics of rx/tx queues with queue_id less than
> > RTE_ETHDEV_QUEUE_STAT_CNTRS can be displayed. If there is a certain
> > application scenario that it needs to use 256 or more than 256 queues
> > and display all statistics of rx/tx queue. At this moment, we have to
> > change the macro to be equaled to the queue number.
> > 
> > However, modifying the macro to be greater than 256 will trigger
> > many errors and warnings from test-pmd, PMD drivers and librte_ethdev
> > during compiling dpdk project. But it is possible and permitted that
> > rx/tx queue number is greater than 256 and all statistics of rx/tx
> > queue need to be displayed. In addition, the data type of rx/tx queue
> > number in rte_eth_dev_configure API is 'uint16_t'. So It is unreasonable
> > to use the 'uint8_t' type for variables that control which per-queue
> > statistics can be displayed.

The explanation is too much complex and misleading.
You mean you cannot increase RTE_ETHDEV_QUEUE_STAT_CNTRS
above 256 because it is an 8-bit type?

[...]
> > --- a/lib/librte_ethdev/rte_ethdev.h
> > +++ b/lib/librte_ethdev/rte_ethdev.h
> >   int rte_eth_dev_set_tx_queue_stats_mapping(uint16_t port_id,
> > -		uint16_t tx_queue_id, uint8_t stat_idx);
> > +		uint16_t tx_queue_id, uint16_t stat_idx);
[...]
> >   int rte_eth_dev_set_rx_queue_stats_mapping(uint16_t port_id,
> >   					   uint16_t rx_queue_id,
> > -					   uint8_t stat_idx);
> > +					   uint16_t stat_idx);
[...]
> cc'ed tech-board,
> 
> The patch breaks the ethdev ABI without a deprecation notice from previous 
> release(s).
> 
> It is mainly a fix to the port_id storage type, which we have updated from 
> uint8_t to uint16_t in past but some seems remained for 
> 'rte_eth_dev_set_tx_queue_stats_mapping()' & 
> 'rte_eth_dev_set_rx_queue_stats_mapping()' APIs.

No, it is not related to the port id, but the number of limited stats.

> Since the ethdev library already heavily breaks the ABI this release, I am for 
> getting this fix, instead of waiting the fix for one more year.

If stats can be managed for more than 256 queues, I think it means
it is not limited. In this case, we probably don't need the API
*_queue_stats_mapping which was invented for a limitation of ixgbe.

The problem is probably somewhere else (in testpmd),
that's why I am against this patch.