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

[Nick Piggin <piggin@cyberone.com.au>]

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.