On Thu, Mar 25, 2021 at 7:25 AM Konstantinos Kaffes <kkaffes@xxxxxxxxx> wrote: > > Hello everyone, > > I want to write a multi-threaded AF_XDP server where all N threads can > read from all N NIC queues. In my design, each thread creates N AF_XDP > sockets, each associated with a different queue. I have the following > questions: > > 1. Do sockets associated with the same queue need to share their UMEM > area and fill and completion rings? Yes. In zero-copy mode this is natural since the NIC HW will DMA the packet into a umem that was decided long before the packet was even received. And this is of course before we even get to pick what socket it should go to. This restriction is currently carried over to copy-mode, however, in theory there is nothing preventing supporting multiple umems on the same netdev and queue id in copy-mode. It is just that nobody has implemented support for it. > 2. Will there be a single XSKMAP holding all N^2 sockets? If yes, what > happens if my XDP program redirects a packet to a socket that is > associated with a different NIC queue than the one in which the packet > arrived? You can have multiple XSKMAPs but you would in any case have to have N^2 sockets in total to be able to cover all cases. Sockets are tied to a specific netdev and queue id. If you try to redirect to socket with a queue id or netdev that the packet was not received on, it will be dropped. Again, for copy-mode, it would from a theoretical perspective be perfectly fine to redirect to another queue id and/or netdev since the packet is copied anyway. Maybe you want to add support for it :-). > I must mention that I am using the XDP skb mode with copies. > > Thank you in advance, > Kostis
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