On Fri, Feb 10, 2023 at 12:50 PM Jens Axboe <axboe@xxxxxxxxx> wrote: > > On 2/10/23 1:44 PM, Linus Torvalds wrote: > > On Fri, Feb 10, 2023 at 12:39 PM Jens Axboe <axboe@xxxxxxxxx> wrote: > >> > >> Right, I'm referencing doing zerocopy data sends with io_uring, using > >> IORING_OP_SEND_ZC. This isn't from a file, it's from a memory location, > >> but the important bit here is the split notifications and how you > >> could wire up a OP_SENDFILE similarly to what Andy described. > > > > Sure, I think it's much more reasonable with io_uring than with splice itself. > > > > So I was mainly just reacting to the "strict-splice" thing where Andy > > was talking about tracking the page refcounts. I don't think anything > > like that can be done at a splice() level, but higher levels that > > actually know about the whole IO might be able to do something like > > that. > > > > Maybe we're just talking past each other. > > Maybe slightly, as I was not really intending to comment on the strict > splice thing. But yeah I agree on splice, it would not be trivial to do > there. At least with io_uring we have the communication channel we need. > And tracking page refcounts seems iffy and fraught with potential > issues. > Hmm. Are there any real-world use cases for zero-copy splice() that actually depend on splicing from a file to a pipe and then later from the pipe to a socket (or file or whatever)? Or would everything important be covered by a potential new io_uring operation that copies from one fd directly to another fd? Maybe I'm getting far ahead of myself.
