> From: Jiang, Cheng1 [mailto:cheng1.ji...@intel.com] > Sent: Thursday, 18 August 2022 08.58 > > Hi, > > > -----Original Message----- > > From: Stephen Hemminger <step...@networkplumber.org> > > Sent: Sunday, August 14, 2022 10:58 PM > > > > On Sun, 14 Aug 2022 12:49:19 +0000 > > Cheng Jiang <cheng1.ji...@intel.com> wrote: > > > > > From: Wenwu Ma <wenwux...@intel.com> > > > > > > Similar to the port mirroring function on the switch or router, > this > > > patch also implements an ingress function on the Vhost lib. When > data > > > is sent to a front-end, it will also send the data to its mirror > > > front-end. > > > > > > Signed-off-by: Cheng Jiang <cheng1.ji...@intel.com> > > > Signed-off-by: Wenwu Ma <wenwux...@intel.com> > > > > We already have rte_flow, packet capture, and rx/tx callbacks. > > This seems like re-invention. > > Sorry that I didn't make it clear in the v1 commit message. This port > mirror function is based on async vhost which is accelerated by DMA > device. Compared with other mirror implements: 1. It's targeted for > vhost. 2. The performance is really good. Its use scenario is to let > one front-end(mirror-VM) monitor the traffic of another front-end(VM). > It's different from the things you mentioned above. So, IMO I don't > think it's re-invention. > > Thanks, > Cheng
Thank you for elaborating the use case. In other words: This is a performance optimization for a specific use case. This raises two questions: 1. Please convince us that this is a common use case? 2. What is the performance compared to implementing it at the application level? Overall, I totally agree with Stephen: Port Mirroring was removed from ethdev with the 21.11 release [1] for the reasons mentioned by Stephen. Please don't try to reintroduce it. If the application needs to mirror all (or some) packets, why not just let the application do it? Furthermore, the application might need to mirror the packets to a physical port, and perhaps encapsulate it for remote packet capture. Sampling could also be required. Here's a prediction for you: More features will creep into to this API over time, and it will end up like the ethdev mirroring API being removed because the alternatives are better and more versatile. [1]: https://doc.dpdk.org/guides/rel_notes/release_21_11.html#removed-items
