Pavel Begunkov wrote: > On 4/15/24 16:06, Willem de Bruijn wrote: > > Pavel Begunkov wrote: > >> On 4/14/24 18:07, Willem de Bruijn wrote: > >>> Pavel Begunkov wrote: > >>>> We'll need to associate additional callbacks with ubuf_info, introduce > >>>> a structure holding ubuf_info callbacks. Apart from a more smarter > >>>> io_uring notification management introduced in next patches, it can be > >>>> used to generalise msg_zerocopy_put_abort() and also store > >>>> ->sg_from_iter, which is currently passed in struct msghdr. > >>> > >>> This adds an extra indirection for all other ubuf implementations. > >>> Can that be avoided? > >> > >> It could be fitted directly into ubuf_info, but that doesn't feel > >> right. It should be hot, so does it even matter? > > > > That depends on the workload (working set size)? > >>> On the bright side, > >> with the patch I'll also ->sg_from_iter from msghdr into it, so it > >> doesn't have to be in the generic path. > > > > I don't follow this: is this suggested future work? > > Right, a small change I will add later. Without ops though > having 3 callback fields in uargs would be out of hands. > > >> I think it's the right approach, but if you have a strong opinion > >> I can fit it as a new field in ubuf_info. > > > > If there is a significant cost, I suppose we could use > > INDIRECT_CALL or go one step further and demultiplex > > based on the new ops > > > > if (uarg->ops == &msg_zerocopy_ubuf_ops) > > msg_zerocopy_callback(..); > > Let me note that the patch doesn't change the number of indirect > calls but only adds one extra deref to get the callback, i.e. > uarg->ops->callback() instead of uarg->callback(). Of course. Didn't mean to imply otherwise. > Your snippet > goes an extra mile and removes the indirect call. > > Can I take it as that you're fine with the direction of the > patch? Or do you want me to change anything? It's fine. I want to avoid new paths slowing down existing code where possible. But if this extra deref would prove significant we have a workaround.
