Extended xstats API in ethdev library to allow grouping of stats
logically so they can be retrieved per logical grouping managed
by the application.
Added new functions rte_eth_xstats_get_names_by_id and
rte_eth_xstats_get_by_id using additional arguments (in compare
to rte_eth_xstats_get_names and rte_eth_xstats_get) - array of ids
and array of values.
doc: add description for modified xstats API
Documentation change for new extended statistics API functions.
The old API only allows retrieval of *all* of the NIC statistics
at once. Given this requires a MMIO read PCI transaction per statistic
it is an inefficient way of retrieving just a few key statistics.
Often a monitoring agent only has an interest in a few key statistics,
and the old API forces wasting CPU time and PCIe bandwidth in retrieving
*all* statistics; even those that the application didn't explicitly
show an interest in.
The new, more flexible API allow retrieval of statistics per ID.
If a PMD wishes, it can be implemented to read just the required
NIC registers. As a result, the monitoring application no longer wastes
PCIe bandwidth and CPU time.
Signed-off-by: Kuba Kozak <kubax.kozak@intel.com>
79c913a42f