Unresponsive system

[Janos Dohanics]

On Wed, 29 Mar 2017 04:45:28 +0200
Polytropon <freebsd at edvax.de> wrote:

> On Tue, 28 Mar 2017 16:06:34 -0400, Janos Dohanics wrote:
> > The system is FreeBSD 11.0-STABLE #0 r314885 amd64. It is mostly
> > used to run Cyrus, Postfix, Amavisd, Clamd. Kernel is not
> > customized, except for "ident".
> > 
> > Could this problem be related to the additional swap space provided
> > by a swapfile?
> > 
> > # cat /etc/fstab
> > # Device	Mountpoint	FStype	Options
> > # Dump	Pass#
> > /dev/ada0p2	none		swap	sw
> > 0	0 /dev/ada0p3	/		ufs	rw
> > 1	1 /dev/ada0p4	none		swap
> > sw	0	0 md0		none
> > swap	sw,file=/swapfile,late	0	0
> > 
> > # swapinfo -hm
> > Device          1M-blocks     Used    Avail Capacity
> > /dev/ada0p2           256     241M      15M    94%
> > /dev/ada0p4           750     290M     460M    39%
> > /dev/md0             4096     289M     3.7G     7%
> > Total                5102     820M     4.2G    16%
> > 
> > I'd appreciate your advice.
> 
> Do you have statistics about your CPU and I/O load? Both can
> cause a system to become unresponsive. Using swap will start
> in case the RAM is "full", and because you have three mechanisms
> of swap on the same disk (ada0), this could be the reason: You
> have two swap partitions and a swap file, all of them residing
> on the same disk, and all of them are in use, so that could be
> the reason for I/O load...

Hello Polytropon,

I have no statistics beyond what I have in the logs (maillog,
amavisd.log, messages), plus I have tried to keep an eye on top(1). I
did notice that at times CPU utilization, RAM and swap use (before
adding the 4 GB md(4) device as the attempted remedy) were close to
100%, while mailq(1) kept growing.

You are quite right, I should have thought about I/O load, and I
didn't. I'll do some experimentation.

In the meantime, Google turned up this page which looks relevant to the
error message in my original post:
http://www.leidinger.net/freebsd/dox/kern/html/df/d20/uipc__socket_8c_source.html

Could you please explain?

-- 
Janos Dohanics