John Baldwin wrote:
> > My hunch, which is why I suggested decreasing the number of
> > tags seen by the driver, is that the tagged queues are over
> > used, and this locks the disk up.  My best guess is an off-by-one
> > or an exceptional condition handler that was not an issue until
> > recently, because of a FreeBSD interrupt architecture change
> > having nothing to do with the driver itself (i.e. the reason it
> > only happens under load, and didn't happen under the same load,
> > before).
> Terry, we've had threaded interrupt handlers for over a year and a half
> now.  If the had really broken things in this basic a fashion we wouldn't
> have made it this far with running systems.  Your hypothesis about
> something busted in the tagged queueing code seems sound but blaiming
> this on interrupt threads doesn't make much sense to me.

The problems don't show up, except under extreme loads, with
particular drives.

Therefore, it is still my hunch.  ;^).

Dropping the queue depth to 8 from 16 to attempt to verify my
hunch won't hurt anything, and may find the problem.  It could
still be an off-by-one error in Soren's code, as well (but I
don't think it is).

-- Terry

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