On Mon, Jul 10, 2023 at 6:10 AM shaouai <aoua...@gmail.com> wrote: > > In the implementation of the Go netpoller, `netpollBreak()` attempts to write > 1 byte to `netpollBreakWr`, whereas `netpoll()` reads up to 16 bytes from > `netpollBreakRd`, why 16 bytes rather than 1 byte? > > write up to 1 byte: > https://cs.opensource.google/go/go/+/refs/tags/go1.20.5:src/runtime/netpoll_epoll.go;l=77;drc=c7cc2b94c63af610a29b1b48cfbfb87cb8abf05b > > read up to 16 bytes: > https://cs.opensource.google/go/go/+/refs/tags/go1.20.5:src/runtime/netpoll_epoll.go;l=146;drc=c7cc2b94c63af610a29b1b48cfbfb87cb8abf05b
A single byte will wake up a goroutine sleeping in netpoll, so there is no reason to write more than one byte. If several different goroutines decide to wake up the polling goroutine before the polling goroutine wakes up, they will each write a single byte, and they will all be satisfied by a single wakeup. And, if we don't read all those bytes, there will still be bytes in the pipe and we'll wake up the next time around the poll loop even if we don't have to. So we try to read all of their wakeup bytes at once. The number 16 is arbitrary, based on the assumption that it's not all that likely that more than 16 goroutines will try to wake up the poller simultaneously. Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAOyqgcX61t6hbFvQQiRcaeP3ufweaUHDLxLN_mUi7TwJpEmOyg%40mail.gmail.com.
