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

[Ali Alnubani <alialnu@oss.nvidia.com>]

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Ferruh Yigit
> Sent: Wednesday, October 13, 2021 11:16 PM
> To: Konstantin Ananyev <konstantin.ananyev@intel.com>; dev@dpdk.org;
> jerinj@marvell.com; Ajit Khaparde <ajit.khaparde@broadcom.com>; Raslan
> Darawsheh <rasland@nvidia.com>; Andrew Rybchenko
> <andrew.rybchenko@oktetlabs.ru>; Qi Zhang <qi.z.zhang@intel.com>;
> Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
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> Subject: Re: [dpdk-dev] [PATCH v6 0/6] hide eth dev related structures
> 
> 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.
> 

Tested (on dpdk-next-net/main) single and multi-core packet forwarding performance with testpmd on both ConnectX-5 and ConnectX-6 Dx. I didn't see any noticeable regressions.

Thanks,
Ali