9. ABI and API Deprecation

See the guidelines document for details of the ABI policy. API and ABI deprecation notices are to be posted here.

9.1. Deprecation Notices

  • The ethdev hotplug API is going to be moved to EAL with a notification mechanism added to crypto and ethdev libraries so that hotplug is now available to both of them. This API will be stripped of the device arguments so that it only cares about hotplugging.
  • Structures embodying pci and vdev devices are going to be reworked to integrate new common rte_device / rte_driver objects (see http://dpdk.org/ml/archives/dev/2016-January/031390.html). ethdev and crypto libraries will then only handle those objects so that they do not need to care about the kind of devices that are being used, making it easier to add new buses later.
  • The EAL function pci_config_space_set is deprecated in release 16.04 and will be removed from 16.07. Macros CONFIG_RTE_PCI_CONFIG, CONFIG_RTE_PCI_EXTENDED_TAG and CONFIG_RTE_PCI_MAX_READ_REQUEST_SIZE will be removed. The /sys entries extended_tag and max_read_request_size created by igb_uio will be removed.
  • ABI changes are planned for struct rte_pci_id, i.e., add new field class. This new added class field can be used to probe pci device by class related info. This change should impact size of struct rte_pci_id and struct rte_pci_device. The release 16.04 does not contain these ABI changes, but release 16.07 will.
  • The following fields have been deprecated in rte_eth_stats: ibadcrc, ibadlen, imcasts, fdirmatch, fdirmiss, tx_pause_xon, rx_pause_xon, tx_pause_xoff, rx_pause_xoff
  • The xstats API and rte_eth_xstats struct will be changed to allow retrieval of values without any string copies or parsing. No backwards compatibility is planned, as it would require code duplication in every PMD that supports xstats.
  • ABI changes are planned for adding four new flow types. This impacts RTE_ETH_FLOW_MAX. The release 2.2 does not contain these ABI changes, but release 2.3 will. [postponed]
  • ABI change is planned for the rte_mempool structure to allow mempool cache support to be dynamic depending on the mempool being created needing cache support. Saves about 1.5M of memory per rte_mempool structure by removing the per lcore cache memory. Change will occur in DPDK 16.07 release and will skip the define RTE_NEXT_ABI in DPDK 16.04 release. The code affected is app/test/test_mempool.c and librte_mempool/rte_mempool.[ch]. The rte_mempool.local_cache will be converted from an array to a pointer to allow for dynamic allocation of the per lcore cache memory.
  • ABI will change for rte_mempool struct to move the cache-related fields to the more appropriate rte_mempool_cache struct. The mempool API is also changed to enable external cache management that is not tied to EAL threads. Some mempool get and put calls are removed in favor of a more compact API. The ones that remain are backwards compatible and use the per-lcore default cache if available. This change targets release 16.07.
  • The rte_mempool struct will be changed in 16.07 to facilitate the new external mempool manager functionality. The ring element will be replaced with a more generic ‘pool’ opaque pointer to allow new mempool handlers to use their own user-defined mempool layout. Also newly added to rte_mempool is a handler index. The existing API will be backward compatible, but there will be new API functions added to facilitate the creation of mempools using an external handler. The 16.07 release will contain these changes.
  • The rte_mempool allocation will be changed in 16.07: allocation of large mempool in several virtual memory chunks, new API to populate a mempool, new API to free a mempool, allocation in anonymous mapping, drop of specific dom0 code. These changes will induce a modification of the rte_mempool structure, plus a modification of the API of rte_mempool_obj_iter(), implying a breakage of the ABI.
  • ABI changes are planned for struct rte_port_source_params in order to support PCAP file reading feature. The release 16.04 contains this ABI change wrapped by RTE_NEXT_ABI macro. Release 16.07 will contain this change, and no backwards compatibility is planned.
  • A librte_vhost public structures refactor is planned for DPDK 16.07 that requires both ABI and API change. The proposed refactor would expose DPDK vhost dev to applications as a handle, like the way kernel exposes an fd to user for locating a specific file, and to keep all major structures internally, so that we are likely to be free from ABI violations in future.