Re: [dpdk-dev] [PATCH v6 0/5] Extended xstats API in ethdev library to allow grouping of stats

[Olivier Matz <olivier.matz@6wind.com>]

Hi,

On Thu, 20 Apr 2017 22:31:35 +0200, Thomas Monjalon <thomas@monjalon.net> wrote:
> 13/04/2017 16:59, Kuba Kozak:
> > Extended xstats API in ethdev library to allow grouping of stats logically
> > so they can be retrieved per logical grouping  managed by the application.
> > Changed existing functions rte_eth_xstats_get_names and rte_eth_xstats_get
> > to use a new list of arguments: array of ids and array of values.
> > ABI versioning mechanism was used to support backward compatibility.
> > Introduced two new functions rte_eth_xstats_get_all and
> > rte_eth_xstats_get_names_all which keeps functionality of the previous
> > ones (respectively rte_eth_xstats_get and rte_eth_xstats_get_names)
> > but use new API inside. Both functions marked as deprecated.
> > Introduced new function: rte_eth_xstats_get_id_by_name to retrieve
> > xstats ids by its names.
> > Extended functionality of proc_info application:
> > --xstats-name NAME: to display single xstat value by NAME
> > Updated test-pmd application to use new API.  
> 
> Applied, thanks

I'm adapting my application to the upcoming dpdk 17.05. I see
several problems with this patchset:

- the API of rte_eth_xstats_get() and rte_eth_xstats_get_names()
  has been modified, and from what I see it was not announced.
  It looks that ABI is preserved however.

- the new functions rte_eth_xstats_get_all() and
  rte_eth_xstats_get_names_all() are marked as deprecated, which
  looks strange for new functions.

About the new api:

int rte_eth_xstats_get(uint8_t port_id, uint64_t *ids, uint64_t *values,
       unsigned int n);

int rte_eth_xstats_get_names(uint8_t port_id,
       struct rte_eth_xstat_name *xstats_names, unsigned int size,
       uint64_t *ids);

- the argument "id" is not at the same place

- why having "size" in one function and "n" in the second (it was
  renamed in the patch)?

- the argument "id" should be const

- a table of uint64_t is returned in place of the struct rte_eth_xstat
  table: if no ids are given, the driver cannot return partial or
  disordered stats anymore. See
  513c78ae3fd6 ("ethdev: fix extended statistics name index")


So, I wonder if it wouldn't be more simple to keep the old
API intact (it would avoid unannounced breakage). The new feature
can be implemented in an additional API:

 rte_eth_xstats_get_by_id(uint8_t port_id, const uint64_t *ids,
       uint64_t *values, unsigned int size)
 rte_eth_xstats_get_names_by_id(uint8_t port_id, const uint64_t *ids,
       struct rte_eth_xstat_name *xstats_names, unsigned int size)

Or:

 rte_eth_xstats_get_by_id(uint8_t port_id, const uint64_t *ids,
       struct rte_eth_xstat *values, unsigned int size)
 rte_eth_xstats_get_names_by_id(uint8_t port_id, const uint64_t *ids,
       struct rte_eth_xstat_name *xstats_names, unsigned int size)

 (which would allow to deprecate the old API, but I'm not sure
  we need to)


Can we fix that for 17.05?

Regards,
Olivier