Re: kblockd/1: page allocation failure in 2.6.9

[Frank Steiner]

Hi all,

thanks for caring! I don't fully understand what you are talking about
in detail :-), but maybe I can give some more information that could help.

- If you suspect the gdth driver causing the error, it must be some very
  special situation on this host causing it. We have 2 other hosts
  with the same icp vortex GDT8514RZ controller like the host
  where the kblockd message occured. They all have internal raid1 disks
  (73gb or 146gb). One is our main NFS server (it has two raid1 with 146g
  each) and it has a lot of I/O, sometimes 50GB or more a day with peaks
  up to 200MB per second (reading), and we never saw any kblockd message
  in the logs (I just checked them all).

- there were no messages "around" the kblockd messages in /var/log/messages
  but the usual ones about remote ssh login, cron jobs etc., but the messages
  were all more than 10 minutes "away" before and after the kblockd happened.

- not much I/O can have taken place on the internal disks attached to the
  icp controller when the bug was triggered, because all the I/O for
  e.g. updates or backups happens only in the night for all hosts except
  the NFS servers.

- the host where the error occured is the only one that (in addition to the icp
  controller with the internal raid1) has two external SCSI-to-IDE-Raids
  attached to the adaptec 29160 controller that runs with the aic7xxx modul.

- According to the user working a lot on this host, it is possible that he
  did a dump of a large mysql database on the external SCSI-to-IDE raids
  around the time where the kblockd messages occured. He can't tell
  for sure if it was the same time.
  Since we never had any problems on the other hosts with the icp
  controllers and the gdth module, maybe the bug occurs in the aic7xxx
  module? Or if it occurs in the gdth, maybe it's caused by some interaction
  between the gdth and the aic7xxx driver both accessing the scsi bus?
  The gdth driver is compiled into the kernel, the aic7xxx loads as module.

- I did a "dd if=/dev/sd? of=/dev/null bs=500M" for all disks (sda on gdth,
  sdb and sdc on aic7xxx) to check if it could be some disk error or sth..
  but those dd went fine without triggering the bug.

Don't know if this info helps...

Please let me know if there is something I can do to help finding
the bug. I don't mind to compile a special kernel for this host if I can
turn on some debugging options. I saw some DEBUG_GDTH variable in gdth.c,
but I don't know how to turn this on exactly, would I have to define the
variable in the header file somehow? (Sorry, I'm not very familiar with
C :-() For the aic7xxx I found two config options AIC7XXX_DEBUG_ENABLE
and AIC7XXX_DEBUG_MASK. Could that help you identify the bug if I have all
this enabled when the bug shows up again?

Thanks!

Frank



--
Dipl.-Inform. Frank Steiner   Web:  http://www.bio.ifi.lmu.de/~steiner/
Lehrstuhl f. Bioinformatik    Mail: http://www.bio.ifi.lmu.de/~steiner/m/
LMU, Amalienstr 17            Phone: +49 89 2180-4049
80333 Muenchen, Germany       Fax:              -4054
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