[openfabrics-ewg] Drop in performance on Mellanox MT25204 single port DDR HCA

[Woodruff, Robert J]

Hi Roland/Michael,

One of my coworkers in Champaign is seeing a performance
issue with the latest SVN driver and the OFED 1.1 Mellanox 
driver on certain platforms.

On the older SVN somewhere around 7500 the Mellanox driver
did not save and restore certain PCI registers before a reset.
Somewhere around SVN 8000 a patch was added to save and
restore these registers. However on our Alcolu platform 
this patch causes the MaxReadReq to be set to 128 bytes (rather than
512)
which limits bandwith to 650MBytes/sec. If I remove the
save/restore of these registers (attached patch), the
bandwidth is back to where we would expect it 1250 Mbytes/sec.

Is there some problem with this patch or do you think it is
some BIOS issue in the platform ?

woody
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pci_regs.patch
Type: application/octet-stream
Size: 3100 bytes
Desc: pci_regs.patch
URL: <http://lists.openfabrics.org/pipermail/ewg/attachments/20061002/5989fa18/attachment.obj>