Re: [dpdk-dev] [PATCH v6 0/6] hide eth dev related structures

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 10/13/2021 2:36 PM, Konstantin Ananyev wrote:
> v6 changes:
> - Update comments (Andrew)
> - Move callback related variables under corresponding ifdefs (Andrew)
> - Few nits in rte_eth_macaddrs_get (Andrew)
> - Rebased on top of next-net tree
> 
> v5 changes:
> - Fix spelling (Thomas/David)
> - Rename internal helper functions (David)
> - Reorder patches and update commit messages (Thomas)
> - Update comments (Thomas)
> - Changed layout in rte_eth_fp_ops, to group functions and
>     related data based on their functionality:
>     first 64B line for Rx, second one for Tx.
>     Didn't observe any real performance difference comparing to
>     original layout. Though decided to keep a new one, as it seems
>     a bit more plausible.
> 
> v4 changes:
>   - Fix secondary process attach (Pavan)
>   - Fix build failure (Ferruh)
>   - Update lib/ethdev/verion.map (Ferruh)
>     Note that moving newly added symbols from EXPERIMENTAL to DPDK_22
>     section makes checkpatch.sh to complain.
> 
> v3 changes:
>   - Changes in public struct naming (Jerin/Haiyue)
>   - Split patches
>   - Update docs
>   - Shamelessly included Andrew's patch:
>     https://patches.dpdk.org/project/dpdk/patch/20210928154856.1015020-1-andrew.rybchenko@oktetlabs.ru/
>     into these series.
>     I have to do similar thing here, so decided to avoid duplicated effort.
> 
> The aim of these patch series is to make rte_ethdev core data structures
> (rte_eth_dev, rte_eth_dev_data, rte_eth_rxtx_callback, etc.) internal to
> DPDK and not visible to the user.
> That should allow future possible changes to core ethdev related structures
> to be transparent to the user and help to improve ABI/API stability.
> Note that current ethdev API is preserved, but it is a formal ABI break.
> 
> The work is based on previous discussions at:
> https://www.mail-archive.com/dev@dpdk.org/msg211405.html
> https://www.mail-archive.com/dev@dpdk.org/msg216685.html
> and consists of the following main points:
> 1. Copy public 'fast' function pointers (rx_pkt_burst(), etc.) and
>     related data pointer from rte_eth_dev into a separate flat array.
>     We keep it public to still be able to use inline functions for these
>     'fast' calls (like rte_eth_rx_burst(), etc.) to avoid/minimize slowdown.
>     Note that apart from function pointers itself, each element of this
>     flat array also contains two opaque pointers for each ethdev:
>     1) a pointer to an array of internal queue data pointers
>     2)  points to array of queue callback data pointers.
>     Note that exposing this extra information allows us to avoid extra
>     changes inside PMD level, plus should help to avoid possible
>     performance degradation.
> 2. Change implementation of 'fast' inline ethdev functions
>     (rte_eth_rx_burst(), etc.) to use new public flat array.
>     While it is an ABI breakage, this change is intended to be transparent
>     for both users (no changes in user app is required) and PMD developers
>     (no changes in PMD is required).
>     One extra note - with new implementation RX/TX callback invocation
>     will cost one extra function call with this changes. That might cause
>     some slowdown for code-path with RX/TX callbacks heavily involved.
>     Hope such trade-off is acceptable for the community.
> 3. Move rte_eth_dev, rte_eth_dev_data, rte_eth_rxtx_callback and related
>     things into internal header: <ethdev_driver.h>.
> 
> That approach was selected to:
>    - Avoid(/minimize) possible performance losses.
>    - Minimize required changes inside PMDs.
> 
> Performance testing results (ICX 2.0GHz, E810 (ice)):
>   - testpmd macswap fwd mode, plus
>     a) no RX/TX callbacks:
>        no actual slowdown observed
>     b) bpf-load rx 0 0 JM ./dpdk.org/examples/bpf/t3.o:
>        ~2% slowdown
>   - l3fwd: no actual slowdown observed
> 
> Would like to thank everyone who already reviewed and tested previous
> versions of these series. All other interested parties please don't be shy
> and provide your feedback.
> 
> Konstantin Ananyev (6):
>    ethdev: allocate max space for internal queue array
>    ethdev: change input parameters for rx_queue_count
>    ethdev: copy fast-path API into separate structure
>    ethdev: make fast-path functions to use new flat array
>    ethdev: add API to retrieve multiple ethernet addresses
>    ethdev: hide eth dev related structures
> 

For series,
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>

No performance regression detected on my testing.

I am merging the series to next-net now which helps testing,
but before merging to main repo it will be good to get more
ack and test results (I can squash new tags later).

@Jerin, @Ajit, @Raslan, @Andrew, @Qi, @Honnappa,
Can you please test this set for any possible regression?

Series applied to dpdk-next-net/main, thanks.