Bug 969491 – Please increase kernel.sched_migration_cost in virtual-host profile

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Bug 969491 - Please increase kernel.sched_migration_cost in virtual-host profile

Summary:	Please increase kernel.sched_migration_cost in virtual-host profile

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 6
Classification:	Red Hat
Component:	tuned (Show other bugs)
Sub Component:
Version:	6.4
Hardware:	All Linux

Priority	urgent Severity urgent
Target Milestone:	rc
Target Release:	---
Assigned To:	Jaroslav Škarvada
QA Contact:	Branislav Blaškovič
Docs Contact:

URL:
Whiteboard:
Keywords:

Duplicates:	960816 980893 (view as bug list)
Depends On:
Blocks:	996991 1013812
	Show dependency tree / graph

Reported:	2013-05-31 10:18 EDT by Julio Entrena Perez
Modified:	2014-03-25 08:43 EDT (History)
CC List:	18 users (show)

See Also:
Fixed In Version:
Doc Type:	Bug Fix
Doc Text:	Cause: The kernel.sched_migration_cost tunable is kept on its default (0.5 ms). Consequence: Big virtualization hosts can experience high contention at the run queue lock. Fix: The kernel.sched_migration_cost tunable was increased 10 times in the virtual-host profile. Result: The added tuning eliminates the contention.
Story Points:	---
Clone Of:
Clones:	986149 996991 1013812 (view as bug list)
Environment:
Last Closed:	2013-11-21 06:35:58 EST
Type:	Bug
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
Proposed fix (849 bytes, patch) 2013-07-23 13:23 EDT, Jaroslav Škarvada	no flags	Details \| Diff
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Knowledge Base (Solution)	358033	None	None	None	Never
Red Hat Product Errata	RHBA-2013:1623	normal	SHIPPED_LIVE	tuned bug fix and enhancement update	2013-11-20 16:38:38 EST

Groups: None (edit)

Description Julio Entrena Perez 2013-05-31 10:18:28 EDT

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

Comment 6 Andrew Cathrow 2013-07-22 10:50:25 EDT

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

Comment 8 Jaroslav Škarvada 2013-07-23 13:23:50 EDT

Created attachment 777400 [details]
Proposed fix

Comment 12 Tomas Dosek 2013-11-11 11:03:18 EST

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

Comment 13 errata-xmlrpc 2013-11-21 06:35:58 EST

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

Comment 14 Rik van Riel 2014-03-20 15:01:06 EDT

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

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