[ircd-ratbox] DNS timeouts with kqueue on FreeBSD 5.4 + ULE scheduler

[Jeremy Chadwick]

I would give the poll() method a try on 4.11, instead of kqueue.
The BSD kqueue model on 4.x is quite different than on 5.x.  I realise
the performance difference is quite major (constant polling vs. an event
driven model), but for now finding a workaround would be best.

Bill's comments here on the list are news to me, but I believe him 100%.
There have been major kqueue changes in the RELENG_5 tree, so some
missing code or the like I can totally believe.

I do find it strange that (in my case) adns breaks only with the ULE
scheduler enabled (vs. 4BSD).  Then again, I also see other "oddities"
with ULE enabled on the same machine, such as this:

PID USERNAME    PRI NICE   SIZE    RES STATE    TIME    WCPU     CPU COMMAND
693 mysql        97    0   467M   268M RUN     54.4H 187.50% 187.50% mysqld

Gotta love processes that take up >100% of the CPU, even on a
uniprocessor system.  ;-)

I'll be giving Aaron and account on my 5.4-STABLE box for testing
purposes, so hopefully we can work some of these out.  Additionally I
should probably give him an account on my 4.11-STABLE box as well,
for additional testing.

-- 
| Jeremy Chadwick                                 jdc at parodius.com |
| Parodius Networking                        http://www.parodius.com/ |
| UNIX Systems Administrator                   Mountain View, CA, USA |
| Making life hard for others since 1977.                             |

On Fri, Jun 10, 2005 at 07:46:35PM -0400, Rachel Llorenna wrote:
> I don't know if this is a related issue, but  too have had problems
> with DNS resolution under ircd on FreeBSD 4.11 (however, it might have
> some features backported from the 5.x tree - there weren't such bugs
> before this kernel upgrade.) It seems to affect both ircd-ratbox-2.1.2
> and ircd-hybrid-7.1, so it's probably a very old bug.
> 
> I'll do some more extensive testing and provide a more detailed
> report. The same issue seems to affect all my FreeBSD 4.11 servers,
> although the one running Linux (presumably using RTSIGIO) doesn't seem
> to have any issues. I'm pretty confident that it must be a bug in the
> new kqueue implementation in BSD, but I hope that the
> ircd-hybrid/ircd-ratbox developers can come up with a more permanent
> workaround, since kqueue provides significant performance gain over
> poll.
> 
> I've heard that ircd-hybrid-7.1 can be fixed if you recompile with a
> different event interface (ie, using --enable-poll as suggested), but
> I've yet to see if the same applies to ircd-ratbox.
> 
> On 6/8/05, Jeremy Chadwick <ratbox at jdc.parodius.com> wrote:
> > Version:
> > ircd-ratbox 2.0.8.  I have not tried 2.1.2 (contrib/ does not build
> > on that version).
> > 
> > Description:
> > This is specific to FreeBSD 5.4 (possibly 5.3 too) machines running
> > kernels build with the SCHED_ULE scheduler (vs. the older SCHED_4BSD
> > scheduler, and using ratbox with the kqueue I/O event driver.
> > 
> > My guess is that the ratbox kqueue code is "broken" in some way;
> > ULE has changed pretty significantly between 5.2 and 5.4, so it
> > wouldn't surprise me.
> > 
> > I can confirm that other kqueue applications on 5.4 (such as Apache 2.0
> > with kqueue patches, BIND 9, and MySQL 4.1) all work without problems,
> > 
> > I can provide a machine for testing+debugging, although Lee should
> > already have access to it.  :-)  Drop me a note if you need your passwd
> > reset, Lee...
> > 
> > Workaround:
> > Disable kqueue support by using --enable-poll.
> > 
> > --
> > | Jeremy Chadwick                                 jdc at parodius.com |
> > | Parodius Networking                        http://www.parodius.com/ |
> > | UNIX Systems Administrator                   Mountain View, CA, USA |
> > | Making life hard for others since 1977.                             |
> > 
> > _______________________________________________
> > ircd-ratbox mailing list
> > ircd-ratbox at lists.ratbox.org
> > http://lists.ratbox.org/cgi-bin/mailman/listinfo/ircd-ratbox
> > 
> 
> 
> -- 
> Regards,
> 
> Rachel Llorenna (frequency)