APAR status
Closed as program error.
Error description
Error Message: The performance problem will show up as poor execution performance on a computationally bound workload running in a relatively tight iterative loop. Profiling will show large amounts of execution time spent at high method offsets running cold code. . Stack Trace: N/A .
Local fix
This issue can be worked around by applying the following Java option to methods which may be suffering from this problem: -Xjit:{package/Class.method(signature)}(disableLoopVersioner) This option will, in general, cause noticeable performance degradation in correctly optimized methods and should be used with great care.
Problem summary
The Loop Versioner optimization in the JIT compiler attempts to speed up loop execution by speculatively moving tests out of a loop body when they can be conservatively tested in a loop invariant manner ahead of the loop. In some circumstances it was possible for these optimizations to create a mutually exclusive sequence of tests leading to the hot loop being recognized as dead code and the unoptimized loop being executed at runtime.
Problem conclusion
The loop related optimizations in the JIT compiler have been enhanced to avoid generating conflicting tests to allow the optimized loop to execute to the greatest extent possible. . This APAR will be fixed in the following Java Releases: 7 SR10 (7.0.10.0) 8 SR2 FP10 (8.0.2.10) 6 SR16 FP20 (6.0.16.20) . Contact your IBM Product's Service Team for these Service Refreshes and Fix Packs. For those running stand-alone, information about the available Service Refreshes and Fix Packs can be found at: https://www.ibm.com/developerworks/java/jdk/
Temporary fix
Comments
APAR Information
APAR number
IV80558
Reported component name
JIT
Reported component ID
620700124
Reported release
260
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2016-01-19
Closed date
2016-01-19
Last modified date
2016-01-19
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fix information
Fixed component name
JIT
Fixed component ID
620700124
Applicable component levels
R260 PSY
UP
R130 PSY
UP
R600 PSY
UP
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Document Information
Modified date:
19 January 2016