HEADS UP: New ZFS in the tree.

[Peter Schuller]

I just upgraded my workstation to CURRENT for the purpose of testing
ZFS. I wanted to report one anomoly that I have seen so far, that I
never saw before and that I do not recognize from other posts.

I had ktorrent seemingly hang. The process is in state TL, and does
not respond to SIGKILL. SIGCONT also has no effect; neither has
SIGSTOP followed by SIGCONT.

Though I do not know how ktorrent works internally, the typical
behavior, and behavior that I saw just prior to this hang, is one of
periodically flushing out a lot of (bittorrent, not file system)
blocks. This happens to the point that the pool is more or less
saturated for the duration of these bursts (when downloading quickly;
around 10 MB/sec in this case). So possibly the triggering factor is
quick writing of a lot of randomly located blocks in a handful of
files.

The current kernel has WITNESS/INVARIATNS, but I did not see anyting
in dmesg subsequent or just prior to this hang.

Both the pool and the file system seem fully functional; this is
distinct from the "hang in zfs state" issue that I see every now and
then on 7.0 whereby the affect ZFS file systems will be completely
inoperable (but not the entire pool).

The sources were cvsup:ed late yesterday. The pool consists of two
mirrored vdev:s with one hot spare. The on-disk format is 6 (I have
not yet upgrade:d the pool nor any file systems).

This is on an amd64 dual-core system with 4 GB:s of RAM. No ZFS
related loader variables remain in loader.conf (I let it auto-tune the
ARC to around 600 MB).

The file system on which ktorrent was doing it's bulk I/O has its
recordsize set to 8 kb, but is otherwise standard (no compression or
funny options).

-- 
/ Peter Schuller

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