Re: [PATCH] per-backing dev unplugging #2

[Jeremy Higdon <jeremy@sgi.com>]

On Tue, Mar 16, 2004 at 08:38:50AM +0100, Jens Axboe wrote:
> On Mon, Mar 15 2004, Jeremy Higdon wrote:
> > > I wonder why nobody's complained about this before?
> >
> > Well, some of us have, but probably not very loudly.  I had
> > naively believed that the global unplug was gone in 2.6.
> 
> Ditching plugging at the water cooler doesn't count as complain, it
> needs to get out in the open :-). When Intel posted their patch and

I agree.  It's one of those little assumptions that one should not
make, but one ends up making anyway.  :-)  Jbarnes did a prototype
of per-queue plug/unplug a couple of years ago for LK2.4, but we
didn't see much benefit.  Obviously, we gave up too soon.

> numbers, that was the first I heard of it.

One problem we had is that the profiling tools on IA64 are
very poor, so we couldn't really tell where the problem was.

jeremy