On 9/28/2020 12:01 PM, Bruce Richardson wrote:
On Mon, Sep 28, 2020 at 11:25:34AM +0100, Ferruh Yigit wrote:
On 9/28/2020 8:31 AM, Dumitru Ceara wrote:
On 9/22/20 4:21 PM, Ferruh Yigit wrote:
On 9/18/2020 11:36 AM, Dumitru Ceara wrote:
Even though ring interfaces don't support any other TX/RX offloads they
do support sending multi segment packets and this should be advertised
in order to not break applications that use ring interfaces.
Does ring PMD support sending multi segmented packets?
Yes, sending multi segmented packets works fine with ring PMD.
Define "works fine" :)
All PMDs can put the first mbuf of the chained mbuf to the ring, in that
case what is the difference between the ones supports
'DEV_TX_OFFLOAD_MULTI_SEGS' and the ones doesn't support?
If the traffic is only from ring PMD to ring PMD, you won't recognize the
difference between segmented or not-segmented mbufs, and it will look like
segmented packets works fine.
But if there is other PMDs involved in the forwarding, or if need to process
the packets, will it still work fine?
What other PMDs do or don't do should be irrelevant here, I think. The fact
that multi-segment PMDs make it though the ring PMD in valid form should be
sufficient to mark it as supported.
As far as I can see ring PMD doesn't know about the mbuf segments.
Right, the PMD doesn't care about the mbuf segments but it implicitly
supports sending multi segmented packets. From what I see it's actually
the case for most of the PMDs, in the sense that most don't even check
the DEV_TX_OFFLOAD_MULTI_SEGS flag and if the application sends multi
segment packets they are just accepted.
As far as I can see, if the segmented packets sent, the ring PMD will put
the first mbuf into the ring without doing anything specific to the next
segments.
If the 'DEV_TX_OFFLOAD_MULTI_SEGS' is supported I expect it should detect
the segmented packets and put each chained mbuf into the separate field in
the ring.
Why, what would be the advantage of that? Right now if you send in a valid
packet chain to the Ring PMD, you get a valid packet chain out again the
other side, so I don't see what needs to change about that behaviour.
Got it. Konstantin also had similar comment, I have replied there.
However, the fact that the ring PMD doesn't advertise this implicit
support forces applications that use ring PMD to have a special case for
handling ring interfaces. If the ring PMD would advertise
DEV_TX_OFFLOAD_MULTI_SEGS this would allow upper layers to be oblivious
to the type of underlying interface.
This is not handling the special case for the ring PMD, this is why he have
the offload capability flag. Application should behave according capability
flags, not per specific PMD.
Is there any specific usecase you are trying to cover?
