Bug 1550573

Summary:	cpu-partitioning: variable no_rebalance_cores doesn't work
Product:	Red Hat Enterprise Linux 7	Reporter:	Tereza Cerna <tcerna>
Component:	tuned	Assignee:	Jaroslav Škarvada <jskarvad>
Status:	CLOSED ERRATA	QA Contact:	Tereza Cerna <tcerna>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	7.5	CC:	jeder, jskarvad, olysonek
Target Milestone:	rc	Keywords:	Patch, Upstream
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	tuned-2.10.0-0.1.rc1.el7	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2018-10-30 10:50:19 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Tereza Cerna 2018-03-01 13:44:35 UTC

Description of problem:
=======================

This is new bug for problem found in:
  https://bugzilla.redhat.com/show_bug.cgi?id=1497182#c19

Currently there are mentioned in /etc/tuned/cpu-partitioning-variables.conf:

  # isolated_cores=2,4-7
  # isolated_cores=2-23
  #
  # To disable the kernel load balancing in certain isolated CPUs:
  # no_rebalance_cores=5-10

but if user uses no_rebalance_cores variable, feature doesn't work. But if he uses no_balance_cores, it works.

There are two options:

  1] Name of 'no_rebalance_cores' variable in /etc/tuned/cpu-partitioning-
     variables.conf is wrong and we need to modify this file to:

      # To disable the kernel load balancing in certain isolated CPUs:
      # no_balance_cores=5-10

  2] Name of 'no_rebalance_cores' is right and it is necessary to modify code
     for using this variable.

Version-Release number of selected component (if applicable):
=============================================================
tuned-2.9.0-1.el7 

Steps to Reproduce:
===================
Use 'no_rebalance_cores' variable:

# cat /etc/tuned/cpu-partitioning-variables.conf
isolated_cores=1-3
no_rebalance_cores=2
# tuned-adm profile cpu-partitioning
# reboot

# cat /run/tuned/no-rebalance-cpus.txt 
#
# cat /proc/sys/kernel/sched_domain/cpu0/domain*/flags
559
4143
# cat /proc/sys/kernel/sched_domain/cpu1/domain*/flags
559
4143
# cat /proc/sys/kernel/sched_domain/cpu2/domain*/flags
559
4143
# cat /proc/sys/kernel/sched_domain/cpu3/domain*/flags
559
4143

Expected results:
=================
When I used 'no_balance_cores' variable, it works:

# cat /etc/tuned/cpu-partitioning-variables.conf
isolated_cores=1-3
no_balance_cores=2
# tuned-adm profile cpu-partitioning
# reboot

# cat /run/tuned/no-rebalance-cpus.txt 
2
# cat /proc/sys/kernel/sched_domain/cpu0/domain*/flags
559
4143
# cat /proc/sys/kernel/sched_domain/cpu1/domain*/flags
559
4143
# cat /proc/sys/kernel/sched_domain/cpu2/domain*/flags
558
4142
# cat /proc/sys/kernel/sched_domain/cpu3/domain*/flags
559
4143

Comment 2 Jaroslav Škarvada 2018-03-01 13:48:10 UTC

I fixed the comment yesterday in:
https://github.com/redhat-performance/tuned/commit/280ac3d3f942b13a59fe9362bfcd2214c08574cf

because I think it's typo, but let's wait for conclusion in bug 1497182.

Comment 3 Ondřej Lysoněk 2018-03-01 14:12:18 UTC

(In reply to Jaroslav Škarvada from comment #2)
> because I think it's typo, but let's wait for conclusion in bug 1497182.

Number of occurences of 'balance': 6
Number of occurences of 'rebalance': 9

I would hardly call that a typo, rather an inconsistency.

Comment 4 Jaroslav Škarvada 2018-03-01 14:58:39 UTC

Luiz, the original author of the feature, seems to agree with keeping the 'no_balance_cores'.

My opinion is that the fix of the comment is not worth the z-stream, so moving to 7.6. Feel free to propose if your opinion vary.

Comment 6 Tereza Cerna 2018-03-12 09:54:58 UTC

Info for QE:
============

According to previous discussion in this bug and BZ#1497182, variable name is finally "no_balance_cores" and all occurences of "rebalance" is fixed in:
 * https://github.com/redhat-performance/tuned/commit/280ac3d3f942b13a59fe9362bfcd2214c08574cf
 * https://github.com/redhat-performance/tuned/commit/d76dc3d62bdd6cf77b51ef2722a69b062f61e195

Comment 8 Tereza Cerna 2018-07-25 11:17:55 UTC

======================================================
Verified in:
    tuned-2.10.0-1.el7.noarch
    tuned-profiles-cpu-partitioning-2.10.0-1.el7.noarch
PASS
======================================================

# cat /etc/tuned/cpu-partitioning-variables.conf 
# Examples:
# isolated_cores=2,4-7
# isolated_cores=2-23
#
# To disable the kernel load balancing in certain isolated CPUs:
# no_balance_cores=5-10                                            !!!! RIGHT HELP !!!!

# echo "isolated_cores=1-3" > /etc/tuned/cpu-partitioning-variables.conf 
# echo "no_balance_cores=2" >> /etc/tuned/cpu-partitioning-variables.conf 

# tuned-adm profile cpu-partitioning

# reboot

# cat /run/tuned/no-balance-cpus.txt                               !!!! FILE EXISTS !!!!
2

# cat /proc/sys/kernel/sched_domain/cpu1/domain*/flags
559
4143
# cat /proc/sys/kernel/sched_domain/cpu2/domain*/flags             !!!! FUNCTIONALITY WORKS !!!!
558
4142
# cat /proc/sys/kernel/sched_domain/cpu3/domain*/flags
559
4143

======================================================
Reproduced in:
    tuned-2.9.0-1.el7.noarch
    tuned-profiles-cpu-partitioning-2.9.0-1.el7.noarch
FAIL
======================================================

# cat /etc/tuned/cpu-partitioning-variables.conf 
# Examples:
# isolated_cores=2,4-7
# isolated_cores=2-23
#
# To disable the kernel load balancing in certain isolated CPUs:
# no_rebalance_cores=5-10                                !!!! WRONG DIRECTIVE !!!!

# echo "isolated_cores=1-3" > /etc/tuned/cpu-partitioning-variables.conf 
# echo "no_rebalance_cores=2" >> /etc/tuned/cpu-partitioning-variables.conf 

# tuned-adm profile cpu-partitioning

# reboot

# cat /run/tuned/no-rebalance-cpus.txt                   !!!! NOT EXISTING FILE !!!!

# cat /proc/sys/kernel/sched_domain/cpu1/domain*/flags
559
4143
# cat /proc/sys/kernel/sched_domain/cpu2/domain*/flags   !!!! FUNCTIONALITY DON'T WORK !!!!
559
4143
# cat /proc/sys/kernel/sched_domain/cpu3/domain*/flags
559
4143

Comment 10 errata-xmlrpc 2018-10-30 10:50:19 UTC

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.

https://access.redhat.com/errata/RHBA-2018:3172