I am testing the performances of geophysical dynamics codes
on a cluster of Opteron 2p boxes with PGI CDK 6.
Until few weeks ago the environment was based
on 2.4.21 Linux kernel.
A migration to the new kernel 2.6.9 was done to the system
since most people reports it is quite beneficial for
the NUMA-ness of the Opteron architecture.
However, I observe a drop in performance of 10-20%.
Any hints about possible sources of this unexpected behaviour ?
PGI is 6.0-2 64-bit target on x86-64 Linux
Linux is 2.6.9-5.0.5.ELsmp
the code is Fortran 77/90 + MPI with optimization flags:
-byteswapio -r8 -Mnodclchk -Mextend -Ktrap=fp
-tp k8-64 -pc=64 -fastsse -O3 -Msmart -Kieee -Mvect=cachesize:1048576,transform
Many thanks for the help