Efficient Event Handling In Linux?

Hey all. I've been looking at efficient event-handling mechanisms (for I/O on sockets, disk, devices) ... As far as I could tell ... the discussion [on linux-kernel] trailed off without any real resolution as to what would actually be done to empower Linux with efficient event handling; perhaps I missed it, but I couldn't find Linus's get_events/bind_event calls, nor could I find /dev/poll or kqueue-styled interfaces integrated

into the latest kernel.
I did find what looks to be an excellent patch in the way of /dev/epoll (written up here:
http://www.xmailserver.org/linux-patches/nio-improve.html). According to the benchmarks he's got, the patch really spanks /dev/poll and POSIX SIGIO. I'm going to begin testing with it soon and was hoping to get some feel for whether /dev/epoll might end up in the kernel mainstream at some point in the not-too-distant future?

Quoted 5 lines · David E. Weekly

Hey all. I've been looking at efficient event-handling mechanisms (for I/O
on sockets, disk, devices) ... As far as I could tell ... the discussion [on linux-kernel] trailed off without any real resolution as to what would actually be done to empower Linux with efficient event handling;
perhaps I missed it, but I couldn't find Linus's get_events/bind_event
calls, nor could I find /dev/poll or kqueue-styled interfaces integrated

Quoted 9 lines

into the latest kernel.
I did find what looks to be an excellent patch in the way of /dev/epoll (written up here:
http://www.xmailserver.org/linux-patches/nio-improve.html). According to the benchmarks he's got, the patch really spanks /dev/poll and POSIX SIGIO. I'm going to begin testing with it soon and was hoping to get some feel for whether /dev/epoll might end up in the kernel mainstream at some point in the not-too-distant future?

My impression is that /dev/epoll is the best for sockets at the moment, and that several people are using it happily now. (The interface is still in flux, I think, so only use it now if you don't mind that.)

However, for disk I/O, IMHO you really want aio instead.
If you need aio now, SGI's kaio patch is available and is said to work well (and heck, there's also a userland emulation in glibc, but I suspect it doesn't perform well). For the future, Ben LaHaise's aio may have better performance when it's done
( http://uwsg.iu.edu/hypermail/linux/kernel/0102.0/0459.html );
he's going to do things like async sendfile, and is willing to provide a nonposix
interface for those who don't want signal delivery's overhead
(see http://uwsg.iu.edu/hypermail/linux/kernel/0102.0/0384.html
and http://www.kvack.org/~blah/aio/v2.4.5-ac9-bcrl4-aio.diff )

I suspect both /dev/epoll and LaHaise's aio will end up being integrated into the stock 2.5 kernel. And if we're really lucky, there will be a single integrated event stream for both. I'm quite annoyed that Posix defines separate polling methods for file descriptors
and aio completions (http://www.opengroup.org/onlinepubs/7908799/xsh/aio_suspend.html);
if one simple interface can handle both, we ought to try to do it.

- Dan "but I play one on TV" Kegel