On Wed, Sep 1, 2021 at 3:42 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: > > John Fastabend <john.fastabend@xxxxxxxxx> writes: > > > Cong Wang wrote: > >> On Tue, Aug 24, 2021 at 4:47 PM Martin KaFai Lau <kafai@xxxxxx> wrote: > >> > Please explain more on this. What is currently missing > >> > to make qdisc in struct_ops possible? > >> > >> I think you misunderstand this point. The reason why I avoid it is > >> _not_ anything is missing, quite oppositely, it is because it requires > >> a lot of work to implement a Qdisc with struct_ops approach, literally > >> all those struct Qdisc_ops (not to mention struct Qdisc_class_ops). > >> WIth current approach, programmers only need to implement two > >> eBPF programs (enqueue and dequeue). > >> > >> Thanks. > > > > Another idea. Rather than work with qdisc objects which creates all > > these issues with how to work with existing interfaces, filters, etc. > > Why not create an sk_buff map? Then this can be used from the existing > > egress/ingress hooks independent of the actual qdisc being used. > > I agree. In fact, I'm working on doing just this for XDP, and I see no > reason why the map type couldn't be reused for skbs as well. Doing it > this way has a couple of benefits: I do see a lot of reasons, for starters, struct skb_buff is very different from struct xdp_buff, any specialized map can not be reused. I guess you are using a generic one, how do you handle the refcnt at least for skb? > > - It leaves more flexibility to BPF: want a simple FIFO queue? just > implement that with a single queue map. Or do you want to build a full > hierarchical queueing structure? Just instantiate as many queue maps > as you need to achieve this. Etc. Please give an example without a queue. ;) Queue is too simple, show us something more useful please. How do you plan to re-implement EDT with just queues? > > - The behaviour is defined entirely by BPF program behaviour, and does > not require setting up a qdisc hierarchy in addition to writing BPF > code. I have no idea why you call this a benefit, because my goal is to replace Qdisc's, not to replace any other things. You know there are plenty of Qdisc's which are not implemented in Linux kernel. > > - It should be possible to structure the hooks in a way that allows > reusing queueing algorithm implementations between the qdisc and XDP > layers. XDP has no skb but xdp_buff, no? And again, why only queues? Thanks.
