Re: [RFC] block layer support for DMA IOMMU bypass mode II

[Andi Kleen]

On Tue, 08 Jul 2003 15:23:14 -0700 (PDT)
"David S. Miller" <[e-mail]> wrote:

>    From: Grant Grundler <[e-mail]>
>    Date: Tue, 8 Jul 2003 16:25:45 -0600
> 
>    On Tue, Jul 08, 2003 at 03:04:33PM -0700, David S. Miller wrote:
>    >    Do you know a common PCI block device that would benefit from this
>    >    (performs significantly better with short sg lists)? It would be
>    >    interesting to test.
>    >    
>    > %10 to %15 on sym53c8xx devices found on sparc64 boxes.
>    
>    Which workload?
> 
> dbench type stuff, but that's a hard thing to test these days with
> the block I/O schedulers changing so much.  Try to keep that part
> constant in the with/vs/without VIO_VMERGE!=0 testing :)

With MPT-Fusion and reaim "new dbase" load it seems to be slightly faster
with forced IOMMU merging on Opteron, but the differences are quite small (~4%) and could
be measurement errors.

-Andi