Created attachment 79701 [details]
The cputimes/load reported from top/ps etc. report extreme loads on kernel processes migration/x. The problem isn't permanent as it takes a while to set off, but once it does it escalates and never stops.
I am unable to locate what's triggering it, but I did a bisect and found the commit at fault:
commit d670ec13178d0fd8680e6742a2bc6e04f28f87d8 - posix-cpu-timers: Cure SMP wobbles.
The load reported doesn't seem real, as there's no sign that the system is under heavy load or unresponsive.
Compiling with CONFIG_NO_HZ=N seems to help for some, but I've only seen a delay in the triggering of it.
Steps to Reproduce:
1. Boot normally with kernel >= 3.0.7
2. Wait ~1 hour (unable to figure out what sets it off. Idle vs full load doesn't seem to matter)
Cpuload/cputime on some migration/x kernel processes show a constant load between 20-100%. Cpu frequency scaling (ondemand) seems to be affected as it never scales down the cores/threads affected.
Report normal load on migration processes. Allow ondemand to scale down.
The bug was first reported here: https://bugs.gentoo.org/show_bug.cgi?id=394487
Adding PeterZ, since he might have more context.
The issue seems to be resolved with version >=3.6.11. Changing status to resolved.