[dpdk-dev] usages issue with external mempool

[Hemant Agrawal]

Hi,
               There was lengthy discussions w.r.t external mempool patches. However, I am still finding usages issue with the agreed approach.

The existing API to create packet mempool, "rte_pktmbuf_pool_create" does not provide the option to change the object init iterator. This may be the reason that many applications (e.g. OVS) are using rte_mempool_create to create packet mempool  with their own object iterator (e.g. ovs_rte_pktmbuf_init).

e.g the existing usages are:
        dmp->mp = rte_mempool_create(mp_name, mp_size, MBUF_SIZE(mtu),
                                     MP_CACHE_SZ,
                                     sizeof(struct rte_pktmbuf_pool_private),
                                     rte_pktmbuf_pool_init, NULL,
                                     ovs_rte_pktmbuf_init, NULL,
                                    socket_id, 0);


With the new API set for packet pool create, this need to be changed to:

        dmp->mp = rte_mempool_create_empty(mp_name, mp_size, MBUF_SIZE(mtu),
                                     MP_CACHE_SZ,
                                     sizeof(struct rte_pktmbuf_pool_private),
                                     socket_id, 0);
                              if (dmp->mp == NULL)
                                             break;

                              rte_errno = rte_mempool_set_ops_byname(dmp-mp,
                                                            RTE_MBUF_DEFAULT_MEMPOOL_OPS, NULL);
                              if (rte_errno != 0) {
                                             RTE_LOG(ERR, MBUF, "error setting mempool handler\n");
                                             return NULL;
                              }
                              rte_pktmbuf_pool_init(dmp->mp, NULL);

                              ret = rte_mempool_populate_default(dmp->mp);
                              if (ret < 0) {
                                             rte_mempool_free(dmp->mp);
                                             rte_errno = -ret;
                                             return NULL;
                              }

                              rte_mempool_obj_iter(dmp->mp, ovs_rte_pktmbuf_init, NULL);

This is not a user friendly approach to ask for changing 1 API to 6 new APIs. Or, am I missing something?

I think, we should do one of the following:

1. Enhance "rte_pktmbuf_pool_create" to optionally accept "rte_mempool_obj_cb_t *obj_init, void *obj_init_arg" as inputs. If obj_init is not present, default can be used.
2. Create a new wrapper API (e.g. e_pktmbuf_pool_create_new) with  the above said behavior e.g.:
/* helper to create a mbuf pool */
struct rte_mempool *
rte_pktmbuf_pool_create_new(const char *name, unsigned n,
               unsigned cache_size, uint16_t priv_size, uint16_t data_room_size,
rte_mempool_obj_cb_t *obj_init, void *obj_init_arg,
               int socket_id)
3. Let the existing rte_mempool_create accept flag as "MEMPOOL_F_HW_PKT_POOL". Obviously, if this flag is set - all other flag values should be ignored. This was discussed earlier also.

Please share your opinion.

Regards,
Hemant