[dpdk-dev] [ovs-dev] [PATCH RFC] dpif-netdev: Add support Intel DPDK based ports.

Vincent JARDIN vincent.jardin at 6wind.com
Wed Jan 29 11:26:58 CET 2014

Hi Thomas,

On 29/01/2014 09:15, Thomas Graf wrote:

 > The obvious and usual best practise would be for DPDK to guarantee
 > ABI stability between minor releases.
 > Since dpdk-dev is copied as well, any comments?

DPDK's ABIs are not Kernel's ABIs, they are not POSIX, there is no 
standard. Currently, there is no such plan to have a stable ABI since we 
need to keep freedom to chase CPU cycles over having a stable ABI. For 
instance, some applications on top of the DPDK process the packets in 
less than 150 CPU cycles (have a look at testpmd:
   http://dpdk.org/browse/dpdk/tree/app/test-pmd )

I agree that some areas could be improved since they are not into the 
critical datapath of packets, but still other areas remain very CPU 
constraints. For instance:
is bad:
    struct eth_dev_ops
is churned, no comment, and a #ifdef that changes the structure 
according to compilation!

Should an application use the librte libraries of the DPDK:
   - you can use RTE_VERSION and RTE_VERSION_NUM :
   - you can write your own wrapper (with CPU overhead) in order to have 
a stable ABI, that wrapper should be tight to the versions of the librte 
=> the overhead is part of your application instead of the DPDK,
   - *otherwise recompile your software, it is opensource, what's the 

We are opened to any suggestion to have stable ABI, but it should never 
remove the options to have fast/efficient/compilation/CPU execution 

Best regards,

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