Bug 1383394 - OpenJDK should default to -XX:+AssumeMP
Summary: OpenJDK should default to -XX:+AssumeMP
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: java-1.8.0-openjdk
Version: 7.4
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Andrew John Hughes
QA Contact: BaseOS QE - Apps
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Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2016-10-10 14:14 UTC by Andrew Haley
Modified: 2016-11-15 03:55 UTC (History)
2 users (show)

Fixed In Version: java-1.8.0-openjdk-1.8.0.111-2.b15.el7_3
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Last Closed: 2016-11-15 03:55:31 UTC
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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.
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