Ubuntu 9.10 / Kernel 2.6.31 - folding performance losses!

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Ubuntu 9.10 / Kernel 2.6.31 - folding performance losses!
Tux is going to explode in your face! We are still running preliminary tests, but it would seem that the kernel included in the RC version of Ubuntu 9.10 "Karmic Koala" - final version due out on Thursday - is causing as major a problem with SMP/A2 as the 2.6.27 kernel did in Ubuntu 8.10. Worse still... 8.10 simply reduced performance by around 25%; performance on an octo-core with 9.10 seems to fall by 63% or more as the number of cores increases!

If this information is confirmed, then it will be highly inadvisable to migrate your Ubuntu 8.04 or 9.04 to the latest version (or to any distribution including kernel version 2.6.31). As usual, it seems that the MPI layer for SMP parallelization with A2 is the cause of this problem. SMP2 is now even more desirable.

You can see the comparison of perfomance between kernel versions, by Frodo the Hobbit, here.

EDIT - October 26th:
Following tests on a dual-core processor running kernel 2.6.31.5, the performance loss has been measured at 6%. This may seem a fairly low amount, but it's much more than we have seen with the 2.6.27 kernel on a dual-core. We'll post the results on the performance loss on a quad-core as soon as we have benchmarked it.