Bug 451100

Note: I don't think this is a kernel problem at all, but Bugzilla forces me to
choose one of 10,000 "components" when I don't have a freaking clue what is
causing this.

My disk periodically starts doing heavy activity.  This usually lasts for 5-8
seconds, and then stops.  It'll usually start up again a few seconds later. 
It'll do this several times in a row, and then stop for a while.... that while
may be 10 seconds, it may be 10 minutes.

During this time, half my desktop becomes unusable.  Firefox and Pidgin both
completely stop responding to any UI inputs.  (Firefox possibly because of the
fsync issue, not sure about Pidgin... I have logging turned off so I can't
imagine what reason it would even need to access the disk.)  Evolution stops
working if I want to move or open new messages.  (Over IMAP, and I don't have
Offline support on, so again, no clue why.)

There is nothing in my logs that indicate any kind of disk/driver issue like I'd
expect from a bad disk or bad controller.

This is relatively recent.  It starts a little over a week ago.  I have not made
any changes to the system, other than removing an IDE DVD drive.

I can't for the life of me find any tool that will tell me WHY the disk is under
such heavy use, all the time, or WHY applications like Pidgin feel the need to
lock up when this is happening.  Powertop just tells me that the sata_nv driver
is responsible for a ton of wakeups, but that's not much of a surprise.

I can hear the disk actually spinning.  The activity light on the computer is
on.  Top does not at all indicate that any application is doing anything,
although it does show Firefox and Pidgin and a couple other apps in (D)iskwait mode.

Most other apps seem to continue working just fine.  I can open up terminals to
run top for example.  Other apps that need to write the disk usually lock up too
(Vim sessions become unusable, likely due to writing their swap files).

I really cannot take any more of this - my computer is barely usable at times
that last for well over 30 minutes, because I get occassionnal fits of
responsive applications lasting only several seconds intermixed with long, long
pauses.

I doubt you can fix this with what I've given you, but if you can tell me what
tools to use to try to debug this, I'd be most happy.  I can't find anything
useful for Linux using Google.  This is where DTrace would come in handy, hmm? :)