Let's say if I'm writing a program in Golang that is similar to the "top" command, which rapidly reads the files under /proc directory (e.g. every 1 second) and I'm launching goroutines to read different parts of that directory. Since /proc is a virtual filesystem not actually stored on the disk, can I assume in this case there won't be any thread blocked? On Friday, May 31, 2024 at 12:34:38 PM UTC-7 Ian Lance Taylor wrote:
> On Fri, May 31, 2024 at 12:09 PM Haoyang Fan <haoyan...@gmail.com> wrote: > > > > I was always under the impression that Go solely uses async I/O under > the hood so that when invoking a seemingly blocking call like os.File.Read > the underlying thread won't be blocked. Go scheduler will save the context > of current goroutine and schedule other goroutines to run on that thread. > This understanding seems to be aligned with most material I can find on the > internet. > > That is how it works for most operations. That said, since you > specifically mentioned os.File.Read, if the os.File is a disk file, > then on most Unix systems the goroutine and the underlying thread will > indeed block for the duration of the I/O. That is because most Unix > systems have no mechanism for non-blocking I/O for disk files, so the > I/O does block the underlying thread. The underlying thread will not > block for I/O on a network connection or a pipe. As a practical > matter this is only relevant when using a networked file system, as > local file systems are fast. > > > However, recently when I was reading the slides ( > https://go.dev/talks/2012/waza.slide#32), on slide 32 I notice it says > "When a goroutine blocks, that thread blocks but no other goroutine > blocks". This is contradictory and make me wonder does Go really perform > I/O in an asynchronous manner (e.g. like select/poll/epoll in Linux) under > the hood? > > > > Can somebody please clarify? > > That talk is from 2012. The network poller and scheduler have been > rewritten since then. > > 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/4e467662-c516-4956-aa76-06f3b244c656n%40googlegroups.com.
