I'm adding netdev to this thread to see if they can help.

I'm seeing an IPoIB (IP over InfiniBand) netperf performance drop off,
of up to 90 MB/s, when using kernels newer than 2.6.11.  This doesn't
appear to be an OpenIB IPoIB issue since the older in-kernel IB for
2.6.11 and a recent svn3687 snapshot both have the same performance (464
MB/s) with 2.6.11.  I used the same kernel config file as a starting
point for each of these kernel builds.  Have there been any changes in
Linux that would explain these results?

Here is the hardware setup and netperf results using 'netperf -f -M -c
-C -H IPoIB_ADDRESS

All benchmarks are with RHEL4 x86_64 with HCA FW v4.7.0
dual EM64T 3.2 GHz PCIe IB HCA (memfull)

Kernel           OpenIB    msi_x  netperf (MB/s)  
2.6.14-rc3      in-kernel    1     374 
2.6.13.2        svn3627      1     386 
2.6.13.2        in-kernel    1     394 
2.6.12.5-lustre in-kernel    1     399  
2.6.12.5        in-kernel    1     402 
2.6.12          in-kernel    1     406 
2.6.12-rc6      in-kernel    1     407
2.6.12-rc5      in-kernel    1     405   <<<<<
2.6.12-rc4      in-kernel    1     470   <<<<<
2.6.12-rc3      in-kernel    1     466 
2.6.12-rc2      in-kernel    1     469 
2.6.12-rc1      in-kernel    1     466
2.6.11          in-kernel    1     464 
2.6.11          svn3687      1     464 
2.6.9-11.ELsmp  svn3513      1     425  (Woody's results, 3.6Ghz EM64T) 

 Thanks,

	- Matt