process hang in zfs->io_ ?

[Peter Schuller]

> I'm running current as of 20080130 on an amd64 box. I can make
> processes stuck in zfs->io_ (output truncated in ddb and top) when I
> make some packages via ports tinderbox. The ports tinderbox access
> local disk via nfs (I also tried nullfs).
> 
> ddb output of ps and alltrace can be found at
> 
> http://www.rafan.org/FreeBSD/zfs/textdump.zfs.20090130.txt
> 
> Any ideas?

A workaround is to disable the ZIL (vfs.zfs.zil_disable="1"), if you
can afford that on the system in question. It will break the
durability of fsync(), but retain it's write barrier semantics.

Btw, does anyone have a good grasp of the status of this bug? I have
seen vague referenced to it being a memory related deadlock for
example, but that's about it. Is the cause known but difficult to fix,
or just unknown?

-- 
/ Peter Schuller

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