Re: [patch] 4GB I/O, cut three

[Jens Axboe <axboe@kernel.org>]

On Wed, May 30 2001, Mark Hemment wrote:
> Hi Jens,
> 
>   I ran this (well, cut-two) on a 4-way box with 4GB of memory and a
> modified qlogic fibre channel driver with 32disks hanging off it, without
> any problems.  The test used was SpecFS 2.0

Cool, could you send me the qlogic diff? It's the one-liner can_dma32
chance I'm interested in, I'm just not sure what driver you used :-)
I'll add that to the patch then. Basically all the PCI cards should
work, I'm just being cautious and only enabling highmem I/O to the ones
that have been tested.

>   Peformance is definitely up - but I can't give an exact number, as the
> run with this patch was compiled with no-omit-frame-pointer for debugging
> any probs.

Good

>   I did change the patch so that bounce-pages always come from the NORMAL
> zone, hence the ZONE_DMA32 zone isn't needed.  I avoided the new zone, as
> I'm not 100% sure the VM is capable of keeping the zones it already has
> balanced - and adding another one might break the camels back.  But as the
> test box has 4GB, it wasn't bouncing anyway.

You are right, this is definitely something that needs checking. I
really want this to work though. Rik, Andrea? Will the balancing handle
the extra zone?

-- 
Jens Axboe