Bug 1506255

Summary: mm: print warning when ksmd thread runs with CONFIG_PREEMPT_RT enabled
Product: Red Hat Enterprise Linux 7 Reporter: Clark Williams <williams>
Component: kernel-rtAssignee: Clark Williams <williams>
kernel-rt sub component: Memory Management QA Contact: Jiri Kastner <jkastner>
Status: CLOSED ERRATA Docs Contact:
Severity: medium    
Priority: unspecified CC: bhu, lgoncalv
Version: 7.5   
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: No Doc Update
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Clone Of: Environment:
Last Closed: 2018-04-10 08:57:57 UTC Type: Bug
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Blocks: 1442258    
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Description Flags
rt: warn when KSM thread runs on PREEMPT_RT none

Description Clark Williams 2017-10-25 13:38:59 UTC 
Description of problem:

Kernel Same-page Merging (CONFIG_KSM) is a mechanism of reducing duplicated pages in the kernel and can reduce memory usage for some cases. Unfortunately the work required to scan physical pages for duplicate contents can result in latency spikes on a real time Linux kernel. 

To warn users of this potential, print a warning when ksmd is activated on a realtime kernel.
Comment 2 Clark Williams 2017-10-30 19:08:34 UTC 
Created attachment 1345569 [details]
rt: warn when KSM thread runs on PREEMPT_RT

First cut at patch to warn when ksmd runs on RT
Comment 7 errata-xmlrpc 2018-04-10 08:57:57 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/RHSA-2018:0676