[dpdk-dev] DSW eventdev and multi-process DPDK

Venky Venkatesh vvenkatesh at paloaltonetworks.com
Fri Dec 21 20:12:04 CET 2018



On 12/21/18, 10:59 AM, "Mattias Rönnblom" <mattias.ronnblom at ericsson.com> wrote:

    On 2018-12-21 19:34, Venky Venkatesh wrote:
    > 
    > 
    > On 12/21/18, 10:24 AM, "Mattias Rönnblom" <mattias.ronnblom at ericsson.com> wrote:
    > 
    >      On 2018-12-21 06:13, Venky Venkatesh wrote:
    >      > Hi,
    >      > We are considering using a multi-process mode of the DPDK with the event generators and consumers being spread across multiple processes (on different cores). We are also considering using the DSW eventdev. Is the DSW designed for such a use case? If so, are there some restrictions and something specific that need to be done to make it work correctly?
    >      >
    >      
    >      The purpose of an event device is to do dynamic load balancing across
    >      multiple cores. Using the DPDK multiple-process support, with its
    >      requirement of having unique, non-overlapping, core masks works against
    >      or even defeats this purpose.
    > 
    > [VV]: I don’t understand your last sentence. Suppose I am having multiple packet processing processes (each with a single thread and polling a disjoint set of queues) and each linked to DSW. Each process would invoke the enqueue which will be handled by the DSW linked to that process. Will the DSWs across these processes "collaborate" to get load balancing across the processes?
    >      
    
    If the processes are to collaborate, and process packets in the same 
    pipeline, they will need to share an event device (for example, a DSW 
    instance).
    
    However, if you put each of your pipeline stages into a process with a 
    single worker thread, you will not leave any room for an event device to 
    load balance, since every eventdev queue will have only a single 
    consumer linked to it.

[VV]: Sorry for the ambiguous terminology used by me -- queue (above) referred to port queues and not eventdev queues. Additionally, consider a very simple pipeline -- just 1 stage followed by transmit. Thus each process is pulling packets out of the port queue, enqueue into local DSW, dequeue from local DSW and running this 1 stage pipeline and transmitting. The role of eventdev in this world is to load balance across the processes -- that is what I meant by DSWs collaborate (since they need to exchange load information and do migration handshake). Hope that clarifies. Pls let me know if this will work. 



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