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Description of problem:
Big virtualization hosts can experience high contention at the run queue lock, please see bug 960816 for more details.

Setting kernel.sched_migration_cost tunable to 5000000 (10X its default value) eliminates the contention.

Please add kernel.sched_migration_cost = 5000000 to "virtual-host" tuned profile.

Version-Release number of selected component (if applicable):
tuned-0.2.19-11.el6.1

How reproducible:
Always.

Steps to Reproduce:
1. Load a big virtualization host with a high number of busy VMs (e.g. host with 32 physical cores, 1TB of RAM running 60 VMs running JBoss).
2. Observe CPU usage, SSH into VMs.

Actual results:
- Unstable TSC warnings.
- High latency in VMs can be observed from a simple SSH session.
- "sleep 5" takes between 7 - 11 seconds to return.
- short softlockups.

Expected results:
VMs run smoothly.

Additional info:
https://bugzilla.redhat.com/show_bug.cgi?id=960816
https://bugzilla.redhat.com/show_bug.cgi?id=825222

*** Bug 980893 has been marked as a duplicate of this bug. ***

Created attachment 777400 [details]
Proposed fix

*** Bug 1028987 has been marked as a duplicate of this bug. ***

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2013-1623.html

*** Bug 960816 has been marked as a duplicate of this bug. ***