Hopefully these questions are not too stupid, but I didn't find any answers looking over the archives of this list or in the io_uring.pdf document. I have an existing C library which is the client part of a client/server network service. It's not exactly the same as HTTP, but it could be thought of as like an HTTP network client where we may hold a few separate TCP/IP connections open to the same server, and we issue multiple requests in flight per TCP connection. There is one pthread per TCP connection usually. I want to try to see if io_uring gives us any performance benefit by seeing if we can use IORING_OP_SENDMSG/IORING_OP_RECVMSG + IOSQE_IO_LINK, as an experiment. (1) How many io_urings should we create? One ring per process? All of the connections share the same ring. Presumably there would be a lot of contention because I suppose we'd need to lock the ring while submitting requests from multiple threads. If there are multiple independent libraries or separate of the program all trying to use io_uring, should they try to share a single ring? One ring per pthread? It seems we could implement this without locks using thread-local storage to hold the the io_uring fd. One ring per physical CPU? (Not sure how to implement this race-free in userspace). One ring per TCP connection? (2) The existing API (which we cannot change) takes user-allocated buffers for the data to read/write. We don't know if these were allocated using malloc, they might be statically allocated or even come from something exotic like mmap of a file. I understand that we cannot register these buffers using IORING_REGISTER_BUFFERS. But can these be passed in the io_uring_sqe->addr field? ie. Do the same restrictions in IORING_REGISTER_BUFFERS also apply to the addr field? Thanks, Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into KVM guests. http://libguestfs.org/virt-v2v
