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Bug 1383394

Summary: OpenJDK should default to -XX:+AssumeMP
Product: Red Hat Enterprise Linux 7 Reporter: Andrew Haley <aph>
Component: java-1.8.0-openjdkAssignee: Andrew John Hughes <ahughes>
Status: CLOSED CURRENTRELEASE QA Contact: BaseOS QE - Apps <qe-baseos-apps>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.4CC: ahughes, jvanek
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: java-1.8.0-openjdk-1.8.0.111-2.b15.el7_3 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2016-11-15 03:55:31 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 Andrew Haley 2016-10-10 14:14:00 UTC 
The number of configures processors can change while a process is running.  If OpenJDK starts with 1 processor and more are added, code is compiled without memory barriers in locks.  This leads to odd behaviour and crashes.

We should always assume that we're running on a multiprocessor system.  This means that we default to safety, but if someone really needs the best performance on a single-core system they can use -XX:-AssumeMP .  RHEL is not certified for single-core usage anyway.
Comment 2 Andrew John Hughes 2016-11-15 03:55:31 UTC 
Closing this as fixed in the current z-stream release.