geli freezing 8.0 RELEASE and 7.2-STABLE

[Wiktor Niesiobedzki]

2009/12/7 Pawel Jakub Dawidek <pjd at freebsd.org>:
> Hi Wiktor:)
>
> My guess is that this is because GELI worker threads are running with
> too high priority (at least for your configuration).
>
> If I am right, the patch below should help you:
>
>        http://people.freebsd.org/~pjd/patches/g_eli.c.2.patch

Hi,

Yes, it looks like it is thread priority problem. With this patch
applied I do not see any freezes nor lags as before. I also did some
small check, how this affects the performance, and I see no
significant change.

I saw some similiar reports here:
http://forums.freebsd.org/showthread.php?t=6230 (though here it is
connected with ZFS and compression).

As far as I can imagine, what happens is, that ZFS usually sends data
to disks as bulk transfers (every 5-10 seconds), so when I'm using
GELI, it has quite a lot of data to encrypt, hence I observe some
lagging. But then, I'm not sure, if compression on ZFS could expose
this scenario in more aparent way.

After having a quick look on
http://www.freebsd.org/doc/en/books/arch-handbook/smp-design.html

Does it mean, that alawys, when we have a a PRIBIO kthread running
(geli thread encrypting data), lower priority processes (esp. userland
processes) will not get any CPU? Sounds bit different than what I
expected...


Cheers,

Wiktor Niesiobedzki