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

From: Mark Hemment (markhe@veritas.com)
Date: Wed May 30 2001 - 04:43:33 EST


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

  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.

  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.

Mark

On Tue, 29 May 2001, Jens Axboe wrote:
> Another day, another version.
>
> Bugs fixed in this version: none
> Known bugs in this version: none
>
> In other words, it's perfect of course.
>
> Changes:
>
> - Added ide-dma segment coalescing
> - Only print highmem I/O enable info when HIGHMEM is actually set
>
> Please give it a test spin, especially if you have 1GB of RAM or more.
> You should see something like this when booting:
>
> hda: enabling highmem I/O
> ...
> SCSI: channel 0, id 0: enabling highmem I/O
>
> depending on drive configuration etc.
>
> Plea to maintainers of the different architectures: could you please add
> the arch parts to support this? This includes:
>
> - memory zoning at init time
> - page_to_bus
> - pci_map_page / pci_unmap_page
> - set_bh_sg
> - KM_BH_IRQ (for HIGHMEM archs)
>
> I think that's it, feel free to send me questions and (even better)
> patches.

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