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Bug 1259043

Summary:	realtime profile: set unboud workqueues cpumask
Product:	Red Hat Enterprise Linux 7	Reporter:	Luiz Capitulino <lcapitulino>
Component:	tuned	Assignee:	Jaroslav Škarvada <jskarvad>
Status:	CLOSED ERRATA	QA Contact:	Tereza Cerna <tcerna>
Severity:	unspecified	Docs Contact:
Priority:	high
Version:	7.2	CC:	bhu, daolivei, hhuang, jeder, jscotka, jskarvad, juzhang, tcerna, tlavigne, xfu
Target Milestone:	rc	Keywords:	ZStream
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	tuned-2.5.1-5.el7	Doc Type:	Enhancement
Doc Text:	Feature: Set the unbound workqueues cpumask to the list of non-isolated cores for the real-time profiles. Reason: The latest RHEL and RT kernels got support for setting the cpumask of unbound workqueues in sysfs, thus we need support for it in the Tuned Realtime profile. Result: Unbound workqueues cpumask is now set to the list of non-isolated cores in the real-time profiles.	Story Points:	---
Clone Of:
Clones:	1282566 (view as bug list)		Environment:
Last Closed:	2016-11-04 07:24:37 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:
Bug Depends On:
Bug Blocks:	1240765, 1273048, 1282566

Description Luiz Capitulino 2015-09-01 20:09:19 UTC

Description of problem:

The latest RHEL and RT kernels got support for setting the cpumask of unbound workqueues in sysfs. For more details, see:

 Bug 1176155 - unbound worker affinity control to be submitted upstream & then backported to RHEL

This patch sets the unbound workqueues cpumask to the list of non-isolated cores for the real-time profiles.

I don't know if this will improve latency numbers as we didn't have any issues with workqueues in the recent past, but it's a good setting to have.

Signed-off-by: Luiz Capitulino <lcapitulino>
---

PS: As far as I could understand the workqueues code, it should be safe
    to drop the writeback cpumask setting line. However, if I do that,
    the writeback cpumask will read "ffff" which either looks like a bug
    in the kernel code or I'm wrong about the global cpumask taking care
    of the writeback workqueue. I'll check this soon, meanwhile I'm not
    dropping working config

 profiles/realtime/tuned.conf | 1 +
 1 file changed, 1 insertion(+)

diff --git a/profiles/realtime/tuned.conf b/profiles/realtime/tuned.conf
index f552818..8688057 100644
--- a/profiles/realtime/tuned.conf
+++ b/profiles/realtime/tuned.conf
@@ -20,6 +20,7 @@ vm.stat_interval = 10
 
 [sysfs]
 /sys/bus/workqueue/devices/writeback/cpumask = ${not_isolated_cpumask}
+/sys/devices/virtual/workqueue/cpumask = ${not_isolated_cpumask}
 /sys/devices/system/machinecheck/machinecheck*/ignore_ce = 1
 
 [bootloader]

Comment 1 Jaroslav Škarvada 2015-10-06 11:42:53 UTC

(In reply to Luiz Capitulino from comment #0)
Thanks, pushed upstream:
https://git.fedorahosted.org/cgit/tuned.git/commit/?id=5a5986bd8bf2db1136b62f168db9255dba1b7a42

Comment 4 Jaroslav Škarvada 2015-11-11 14:27:09 UTC

*** Bug 1251255 has been marked as a duplicate of this bug. ***

Comment 7 Tereza Cerna 2016-08-24 07:23:39 UTC

==============================================
Verified in:
    tuned-2.7.1-2.el7.noarch
    tuned-profiles-realtime-2.7.1-2.el7.noarch
PASS
==============================================

# cat /sys/devices/virtual/workqueue/cpumask
ff
# cat /usr/lib/tuned/realtime/tuned.conf 
...
[sysfs]
/sys/bus/workqueue/devices/writeback/cpumask = ${not_isolated_cpumask}
/sys/devices/virtual/workqueue/cpumask = ${not_isolated_cpumask}
/sys/devices/system/machinecheck/machinecheck*/ignore_ce = 1
...
# cat /etc/tuned/realtime-variables.conf 
isolated_cores=0
# tuned-adm profile realtime
# cat /sys/devices/virtual/workqueue/cpumask
0e

==============================================
Reproduced in:
    tuned-2.5.1-1.el7.noarch
    tuned-profiles-realtime-2.5.1-1.el7.noarch
FAIL
==============================================

# cat /usr/lib/tuned/realtime/tuned.conf 
...
[sysfs]
/sys/bus/workqueue/devices/writeback/cpumask = ${not_isolated_cpumask}
/sys/devices/system/machinecheck/machinecheck*/ignore_ce = 1
...

Comment 9 errata-xmlrpc 2016-11-04 07:24:37 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://rhn.redhat.com/errata/RHBA-2016-2479.html