kern/177536: zfs livelock (deadlock) with high write-to-disk load

[Andriy Gapon]

on 04/04/2013 19:12 Kevin Day said the following:
> 
> On Apr 4, 2013, at 11:07 AM, Andriy Gapon <avg at FreeBSD.org> wrote:
> 
>> on 04/04/2013 19:05 Kevin Day said the following: [a lot]
>> 
>> One link: https://wiki.freebsd.org/AvgZfsDeadlockDebug
> 
> 
> Sorry, should have mentioned i've seen this.
> 
> I've tried procstat, but i've failed at keeping it cached long enough to use it
> when this happens. If I try running it, the shell gets stuck in 'ufs'. I'm
> going to add a cron job to just run procstat periodically so hopefully i can
> run it without it needing to touch the disks.

Well, stuck ufs points towards to the storage subsystem.
You can create a memory disk+fs (see mdconfig, mdmfs) and place some tools there.
That way you may be able to get more info and also check if it's VFS or some other
common that gets stuck or if it's the real storage indeed.

> I built a more debug friendly kernel and tried to drop to ddb when this
> happened, but it didn't provide anything useful. When I hit 'enter' on
> 'alltrace' it hard locked without printing anything.
> 
> I haven't been able to trigger a core dump, and this system has no serial or
> firewire ports for live debugging.
> 
> 


-- 
Andriy Gapon