Re: [Linuxarm] Re: [RFC v2] net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc

[Jason A. Donenfeld]

On Thu, Mar 18, 2021 at 1:33 AM Yunsheng Lin <linyunsheng@xxxxxxxxxx> wrote:
> > That offer definitely still stands. Generalization sounds like a lot of fun.
> >
> > Keep in mind though that it's an eventually consistent queue, not an
> > immediately consistent one, so that might not match all use cases. It
> > works with wg because we always trigger the reader thread anew when it
> > finishes, but that doesn't apply to everyone's queueing setup.
>
> Thanks for mentioning this.
>
> "multi-producer, single-consumer" seems to match the lockless qdisc's
> paradigm too, for now concurrent enqueuing/dequeuing to the pfifo_fast's
> queues() is not allowed, it is protected by producer_lock or consumer_lock.

The other thing is that if you've got memory for a ring buffer rather
than a list queue, we worked on an MPMC ring structure for WireGuard a
few years ago that we didn't wind up using in the end, but it lives
here:
https://git.zx2c4.com/wireguard-monolithic-historical/tree/src/mpmc_ptr_ring.h?h=tg/mpmc-benchmark