Re: [dpdk-dev] [RFC 0/7] hide eth dev related structures

[Jerin Jacob <jerinjacobk@gmail.com>]

On Fri, Aug 20, 2021 at 9:59 PM Konstantin Ananyev
<konstantin.ananyev@intel.com> wrote:
>
> NOTE: This is just an RFC to start further discussion and collect the feedback.
> Due to significant amount of work, changes required are applied only to two
> PMDs so far: net/i40e and net/ice.
> So to build it you'll need to add:
> -Denable_drivers='common/*,mempool/*,net/ice,net/i40e'
> to your config options.

>
> That approach was selected to avoid(/minimize) possible performance losses.
>
> So far I done only limited amount functional and performance testing.
> Didn't spot any functional problems, and performance numbers
> remains the same before and after the patch on my box (testpmd, macswap fwd).


Based on testing on octeonxt2. We see some regression in testpmd and
bit on l3fwd too.

Without patch: 73.5mpps/core in testpmd iofwd
With out patch: 72 5mpps/core in testpmd iofwd

Based on my understanding it is due to additional indirection.

My suggestion to fix the problem by:
Removing the additional `data` redirection and pull callback function
pointers back
and keep rest as opaque as done in the existing patch like [1]

I don't believe this has any real implication on future ABI stability
as we will not be adding
any new item in rte_eth_fp in any way as new features can be added in slowpath
rte_eth_dev as mentioned in the patch.

[2] is the patch of doing the same as I don't see any performance
regression after [2].


[1]
- struct rte_eth_burst_api {
- struct rte_eth_fp {
+ void *data;
  rte_eth_rx_burst_t rx_pkt_burst;
  /**< PMD receive function. */
  rte_eth_tx_burst_t tx_pkt_burst;
@@ -85,8 +100,19 @@ struct rte_eth_burst_api {
  /**< Check the status of a Rx descriptor. */
  rte_eth_tx_descriptor_status_t tx_descriptor_status;
  /**< Check the status of a Tx descriptor. */
+ /**
+ * User-supplied functions called from rx_burst to post-process
+ * received packets before passing them to the user
+ */
+ struct rte_eth_rxtx_callback
+ *post_rx_burst_cbs[RTE_MAX_QUEUES_PER_PORT];
+ /**
+ * User-supplied functions called from tx_burst to pre-process
+ * received packets before passing them to the driver for transmission.
+ */
+ struct rte_eth_rxtx_callback *pre_tx_burst_cbs[RTE_MAX_QUEUES_PER_PORT];
  uintptr_t reserved[2];
-} __rte_cache_min_aligned;
+} __rte_cache_aligned;

[2]
https://pastebin.com/CuqkrCW4