User Freebsd wrote:
On Wed, 19 Jul 2006, Robert Watson wrote:
On Wed, 19 Jul 2006, User Freebsd wrote:
Yes, this was going to be my next question -- if you're seeing
wedges under load and there's a common controller in use, maybe
we're looking at a driver bug. Bugs of those sort typically look a
lot like what you describe: an I/O is "lost" and so eveything that
depends on the I/O wedges waiting for it, leading to a lot of
processes hanging around waiting for vnode locks, etc.
'k, but how do we debug *that*? :( If it was one, I'd suspect
hardware ... but *three*, and only acting up *after* upgrading to
FreeBSD 6.x, and only acting up under load ...
There are two normal approaches:
(1) Switch controllers and see if the problem goes away, then blame the
controller that was replaced. :-)
(2) Debug the driver when the system is in the wedged state. When
Scott Long
helped me out with an identical problem with the 3ware driver a few
years
ago, he basically added debugging output for the driver in the
debugger to
list the state of outstanding I/Os, count the number of in-bound,
out-bound I/Os, etc, to try and find where the missing one was
leaked. My
impression is that once he had confirmed the presence of the
problem, it
was fairly easy to fix, but that confirming it required quite a bit of
paperwork.
'k, first question is with the core file provide any insight into this?
ie. provide further confirmation that it looks like the driver vs file
system?
second question, who is currently maintaining the iir driver? I've CC'd
Achim in this, as he's listed in the man page as being the maintainer ...
Now, uranus has all the various kernel debugging enabled right now, and
a serial console, so we're good for the debugging side of things ... and
I believe that I can fairly easily "recreate" the issue by just moving a
whack of vServers onto that machine to give it the load that seems to
kill it ... *and* uranus is one of my newer machines, so the card that
is in it is fairly new ... but, since I have a full BIOS serial console
working on it, I should be able to get full model # and firmware
version, which I take it will help some?
What exact version of FreeBSD are you dealing with?
Scott
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