Re: Putrid Elevator Behavior 2.4.18/19

[Jens Axboe]

On Tue, Mar 26 2002, Jeff V. Merkey wrote:
> > 
> > That's good news.
> > 
> > Are you still working on the A/B list patch?  I'd imagine that it could make
> > several problems easier to fix in the block layer.
> > 
> 
> Yes.  I am asking Darren Major, who wrote the A/B implementation 
> in NetWare to review the patch before we submit it.  It may affect
> some drivers.  We are verifying that the change I instrumented 
> will not break anything.

I'm curious how you are doing this cleanly in 2.4. There are lots of
places in the kernel that do direct list management on the queue_head.
Are you adding two separate hidden lists and splicing content to the
queue_head?

2.5 has this done much more cleanly (of course I'm very biased). See the
deadline I/O scheduler patch I've posted before, stuff like this can be
done a lot cleaner there. Internal I/O scheduler structures are
completely hidden from drivers.

-- 
Jens Axboe