[mvapich-discuss] how to debug performance degradation in mvapich2-0.9.5

[Christian Guggenberger]

Hi list,

At least for one of our local codes we experience strong performance
degradation, when comparing mvapich2-0.9.5 to mvapich-0.9.8. (with
mvapich2-0.9.5 it's running ~40 % slower)

The nodes involved here are Dual-Opteron nodes, 2GB per CPU, PCI-X 23108
HCA, Mellanox MTS9600 switch. The stack is based on OFED-1.1-rc, linux-kernel
2.6.17 . Both mvapich versions were compiled with the supplied build
scripts. (omitting -DSRQ for mvapich2)

The code in question (Fortran 90) runs on 18 nodes (36 CPUs), taking 1.4 GB per CPU. I have not yet details on the communication pattern of the code.

I'll check if osu_bw and osu_latency can shed light on this issue.

thanks for your suggestions,

cheers.
 - Christian
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