[ofa-general] Performance penalty of OFED 1.1 versus IBGD 1.8.2

[Roland Fehrenbacher]

Hi,

I'm migrating from IBGD 1.8.2 (kernel 2.6.15.7) to OFED 1.1, and saw
some unpleasant performance drops when using OFED 1.1 (kernel 2.6.20.1
with included IB drivers). The main drop is in throughput as measured
by the OSU MPI bandwidth benchmark. However, the latency for large
packet sizes is also worse (see results below). I tried with and
without "options ib_mthca msi_x=1" (using IBGD, disabling msi_x makes
a siginficant performance difference of approx. 10%). The IB card is a
Mellanox MHGS18-XT (PCIe/DDR Firmware 1.2.0) running on an Opteron
with nForce4 2200 Professional chipset.

Does anybody have an explanation or even better a solution to this
issue?

Thanks,

Roland

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