[dpdk-dev] RFC: hiding struct rte_eth_dev
jerinjacobk at gmail.com
Tue Sep 24 18:42:16 CEST 2019
On Mon, Sep 23, 2019 at 9:49 PM Ray Kinsella <mdr at ashroe.eu> wrote:
> Hi folks,
> The ABI Stability proposals should be pretty well known at this point.
> The latest rev is here ...
> As has been discussed public data structure's are risky for ABI
> stability, as any changes to a data structure can change the ABI. As a
> general rule you want to expose as few as possible (ideally none), and
> keep them as small as possible.
> One of the key data structures in DPDK is `struct rte_eth_dev`. In this
> case, rte_eth_dev is exposed public-ally, as a side-effect of the
> inlining of the [rx,tx]_burst functions.
> Marcin Zapolski has been looking at what to do about it, with no current
> consensus on a path forward. The options on our table is:-
> 1. Do nothing, live with the risk to DPDK v20 ABI stability.
> 2. Pad rte_eth_dev, add some extra bytes to the structure "in case" we
> need to add a field during the v20 ABI (through to 20.11).
> 3. Break rte_eth_dev into public and private structs.
> - See
> - This ends up quiet an invasive patch, late in the cycle, however it
> does have no performance penalty.
> 4. Uninline [rx,tx]_burst functions
> - See
> - This has a performance penalty of ~2% with testpmd, impact on a "real
> workload" is likely to be in the noise.
> We need to agree an approach for v19.11, and that may be we agree to do
> nothing. My personal vote is 4. as the simplest with minimal impact.
My preference NOT to do #4. Reasons are:
- I have seen performance drop from 1.5% to 3.5% based on the arm64
cores in use(Embedded vs Server cores)
- We need the correct approach to cater to cryptodev and eventdev as
well. If #4 is checked in, We will
take shotcut for cryptodev and eventdev
My preference #1, do nothing, is probably ok and could live with #2,
and fix properly with #3 as when needed and use #3 scheme for crypto
dev and eventdev as well.
> Ray K
More information about the dev