Greetings,
(please CC replies to me)

After upgrading to 2.6.28 I noticed some latency problems. Mostly, bash 
and other programs would take a second or so to start where earlier it 
would start almost instantly. I have some nice'd tasks that use 100% of 
the CPU on each core of the Core 2 duo, and killing these tasks make the 
latency go away. But with older kernels these tasks did not cause 
latency problems.

I bisected it to f9c0b0950d5fd8c8c5af39bc061f27ea8fddcac3 
"sched: revert back to per-rq vruntime," and reverting it from 2.6.28 
fixes the latency.

Here is config and dmesg output of vanilla 2.6.28. System is x86_64 
Fedora 10. Let me know if there is additional details I can provide. Thanks.

Jayson