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 15:53, Ferruh Yigit:
> On 9/28/2020 10:16 AM, Thomas Monjalon wrote:
> > 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.
> > 
> 
> Right, it is not related to the port id, it is fixing the storage type for index 
> used to map the queue 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.
> > 
> 
> This patch is not to fix queue stats mapping, I agree there are problems related 
> to it, already shared as comment to this set.
> 
> But this patch is to fix the build errors when 'RTE_ETHDEV_QUEUE_STAT_CNTRS' 
> needs to set more than 255. Where the build errors seems around the 
> stats_mapping APIs.

It is not said this API is supposed to manage more than 256 queues mapping.
In general we should not need this API.
I think it is solving the wrong problem.