Re: [Coder-Com] Re: PROBLEM: high system usage / poor SMPnetwork performance

[Dan Kegel <dank@kegel.com>]

Arjen Wolfs wrote:
> The ircu version that supports kqueue and /dev/poll is currently being
> beta-tested on a few servers on the Undernet. The graph at
> http://www.break.net/ircu10-to-11.png shows the load average (multiplied by
> 100) on a on a server with 3000-4000 clients using poll(), and /dev/poll.
> The difference is obviously quite dramatic, and the same effect is being
> seen with kqueue. You could also try some of the /dev/poll patches for
> linux, which migth save you writing a new engine. Note that ircu 2.10.11 is
> still beta though, and is known to crash in mysterious ways from time to time.

None of the original /dev/poll patches for Linux were much
good, I seem to recall; they had scaling problems and bugs.

The /dev/epoll patch is good, but the interface is different enough
from /dev/poll that ircd would need a new engine_epoll.c anyway.
(It would look like a cross between engine_devpoll.c and engine_rtsig.c,
as it would need to be notified by os_linux.c of any EWOULDBLOCK return values.
Both rtsigs and /dev/epoll only provide 'I just became ready' notification, 
but no 'I'm not ready anymore' notification.)

And then there's /dev/yapoll (http://www.distributopia.com), which
I haven't tried yet (I don't think the author ever published the patch?).

Anyway, the new engine wouldn't be too hard to write, and
would let irc run fast without a patched kernel.

- Dan