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SubjectRe: PCI-DMA: Out of IOMMU space on x86-64 (Athlon64x2), with solution
On Thursday 02 March 2006 00:23, Michael Monnerie wrote:
> Hello, I use SUSE 10.0 with all updates and actual kernel 2.6.13-15.8 as
> provided from SUSE (just self compiled to optimize for Athlon64, SMP,
> and HZ=100), with an Asus A8N-E motherboard, and an Athlon64x2 CPU.
> This host is used with VMware GSX server running 6 Linux client and one
> Windows client host. There's a SW-RAID1 using 2 SATA HDs.

Nvidia hardware SATA cannot directly DMA to > 4GB, so it
has to go through the IOMMU. And in that kernel the Nforce
ethernet driver also didn't do >4GB access, although the ethernet HW
is theoretically capable.

Maybe VMware pins unusually much IO memory in flight (e.g. by using
a lot of O_DIRECT). That could potentially cause the IOMMU to fill up.
The RAID-1 probably also makes it worse because it will double the IO
mapping requirements.

Or you have a leak in some driver, but if the problem goes away
after enlarging the IOMMU that's unlikely.

What would probably help is to get a new SATA controller that can
access >4GB natively and at some point update to a newer kernel
with newer forcedeth driver. Or just run with the enlarged IOMMU.

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