On 4/12/22 6:40 PM, Eric Dumazet wrote: > > On 4/12/22 13:26, Jens Axboe wrote: >> Hi, >> >> If we accept a connection directly, eg without installing a file >> descriptor for it, or if we use IORING_OP_SOCKET in direct mode, then >> we have a socket for recv/send that we can fully serialize access to. >> >> With that in mind, we can feasibly skip locking on the socket for TCP >> in that case. Some of the testing I've done has shown as much as 15% >> of overhead in the lock_sock/release_sock part, with this change then >> we see none. >> >> Comments welcome! >> > How BH handlers (including TCP timers) and io_uring are going to run > safely ? Even if a tcp socket had one user, (private fd opened by a > non multi-threaded program), we would still to use the spinlock. But we don't even hold the spinlock over lock_sock() and release_sock(), just the mutex. And we do check for running eg the backlog on release, which I believe is done safely and similarly in other places too. > Maybe I am missing something, but so far your patches make no sense to > me. It's probably more likely I'm missing something, since I don't know this area nearly as well as you. But it'd be great if you could be specific. -- Jens Axboe
