Re: Serious I/O problems (bad performance and live-lock)

> From: "Daniel Eriksson" <daniel_k_eriksson_at_telia.com>
> Date: Fri, 22 Apr 2005 18:55:34 +0200
> Sender: owner-freebsd-current_at_freebsd.org
> 
> Scott Long wrote:
> 
> > Ok, next test would be to turn off mpsafevm.  This is just a simple
> > guess, though, but and changes in the behaviour would be very
> > interesting to note.
> 
> With debug.mpsafevfs="0" and debug.mpsafevm="0" it doesn't seem like I can
> force the machine into live-lock. No matter how long I let 'dd' run I can
> still abort it with CTRL-C easily. However, after a few minutes the machine
> becomes mostly useless because it takes 30-60 seconds to execute simple
> commands such as ps or ls.
> 
> According to 'top', the dd process spend most of its time in "wdrain" state.
> 
> /Daniel Eriksson

This certainly makes something to do with VM seem like the culprit, but
I thought I'd post information on what I am seeing in hopes that it
might help.

I am still seeing the live-locks, too. They seem to happen when I have a
CPU intensive process running. I have seen it with evolution, and
transcode.

The behavior is odd in that some things run fine. I can leave top
running and it updates like normal and accepts commands like kill and
renice. But I can get an interactive prompt either in X or on a
vty. Suspending the CPU intensive process immediately frees up the
live-lock. Running the CPU intensive job a nice 10 does not help. My
Gnome applets are fine and seem to be very responsive. I have seen
gkrellm lock up, but it usually does not.

I am running ULE, so it's not 4BSD specific. I am also running
PREEMPTION. System is an IBM T30 with 1.8 GHz CPU and .5 GB RAM. the
kernel does not include SMP or APIC but does run ACPI.

I am providing this in hopes of narrowing things down. The live-lock
problem is not the cause of the I/O issues I was having with my fxp
Ethernet or with my secondary IDE bus.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman_at_es.net			Phone: +1 510 486-8634