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

[Nick Piggin]

Jeremy Higdon wrote:

> On Tue, Mar 16, 2004 at 05:36:18PM +1100, Nick Piggin wrote:
>
> > Jeremy Higdon wrote:
> >
> >
> > > My tests were on an 8 CPU x 1300 MHz Altix with 64 disks.
> > Nice - so if you had enough IO capacity to saturate the CPUs it
> > might come close to a 4x improvement - and this sounds like one
> > of your baby systems?
>
> Baby by cpu count, mid size by I/O capability.  Extrapolations of
> this sort are fraught with peril.  However, it is conceivable that
> we would end up with 4X the IOPS.

Well, it is more than 2x! What does a profile look like after
the patch, I wonder?

> > 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.

I wasn't talking about SGI in particular, I just remember
people being very worried about making sure we can support
*thousands* of queues quite a while back.

Anyway, it's done now. And Jens' patch turned out to be pretty
simple and probably makes the code cleaner, anyway.

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