Re: [PATCH rdma-next 0/2] Introduce Multi-Packet receive work queue

[Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

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On Wed, Oct 18, 2017 at 12:55:21PM +0300, Sagi Grimberg wrote:
>
> > A Multi-Packet receive WQ comes to improve performance and memory
> > footprint. It is comprised of work requests that can be consumed by
> > multiple packets. Buffers pointed by SGEs of each work request in a
> > multi packet WQ are divided into strides. Both buffer size and stride
> > size must be identical in all work requests of the same multi packet
> > WQ and are set during WQ creation.
> >
> > A single WR in a Multi-Packet WQ can generate multiple completions,
> > depends on the number of packets consumed. Each packet starts at the
> > beginning of a stride and is written in stride granularity.
> >
> > Here is an example of a work request comprised of 3 strides. Packet 1
> > is larger than a stride so it occupies 2 strides. Packet 2 fits in a
> > single stride. Each packet will generate its own completion.
> >
> > |         |         |[packet2]|
> > |    [packet1]      |         |
> > |_________|_________|_________|
> >   stride      stride     stride
> >   <--      work request     -->
> >
> > A Multi-Packet WQ reduces the number of needed post-recv operations
> > thus increasing performance: In the example above, a single post-recv
> > operation was performed instead of 2.
>
> Looks like a nice feature, would be nice if we could use it... The
> problem is that adding a different logic in case this feature exists is
> messy and difficult. Is there any way we can come up with a verbs API
> that will utilize this feature but hide the implementation details from
> the ULPs?

We will be more than happy to work with the community and update our
driver's code if needed, once the community will converge on the proper API.
Right now, we are exposing it through our DV interface.

Thanks

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