On 11/06, Willem de Bruijn wrote: > > > IMHO, we need a better UAPI to receive the tokens and give them back to > > > the kernel. CMSG + setsockopt(SO_DEVMEM_DONTNEED) get the job done, > > > but look dated and hacky :-( > > > > > > We should either do some kind of user/kernel shared memory queue to > > > receive/return the tokens (similar to what Jonathan was doing in his > > > proposal?) > > > > I'll take a look at Jonathan's proposal, sorry, I'm not immediately > > familiar but I wanted to respond :-) But is the suggestion here to > > build a new kernel-user communication channel primitive for the > > purpose of passing the information in the devmem cmsg? IMHO that seems > > like an overkill. Why add 100-200 lines of code to the kernel to add > > something that can already be done with existing primitives? I don't > > see anything concretely wrong with cmsg & setsockopt approach, and if > > we switch to something I'd prefer to switch to an existing primitive > > for simplicity? > > > > The only other existing primitive to pass data outside of the linear > > buffer is the MSG_ERRQUEUE that is used for zerocopy. Is that > > preferred? Any other suggestions or existing primitives I'm not aware > > of? > > > > > or bite the bullet and switch to io_uring. > > > > > > > IMO io_uring & socket support are orthogonal, and one doesn't preclude > > the other. As you know we like to use sockets and I believe there are > > issues with io_uring adoption at Google that I'm not familiar with > > (and could be wrong). I'm interested in exploring io_uring support as > > a follow up but I think David Wei will be interested in io_uring > > support as well anyway. > > I also disagree that we need to replace a standard socket interface > with something "faster", in quotes. > > This interface is not the bottleneck to the target workload. > > Replacing the synchronous sockets interface with something more > performant for workloads where it is, is an orthogonal challenge. > However we do that, I think that traditional sockets should continue > to be supported. > > The feature may already even work with io_uring, as both recvmsg with > cmsg and setsockopt have io_uring support now. I'm not really concerned with faster. I would prefer something cleaner :-) Or maybe we should just have it documented. With some kind of path towards beautiful world where we can create dynamic queues..
