openjdk team mailing list archive

[C Erler <689041@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

When running the attached Java program using the client VM, `(a < 0L)`
is evaluated much more quickly than `(a < Long.MIN_VALUE) ^ (a < 0L)`,
which is what should happen.

However, using the server VM, `(a < 0L)` evaluates slightly *slower*
than `(a < Long.MIN_VALUE) ^ (a < 0L)`.

$ sudo nice -n -15 java -server UnsignedLong 
Useless XOR time: 2.121191887s
Without XOR time: 2.708230708s
Useless XOR time: 2.552766027s
Without XOR time: 2.601783612s
Useless XOR time: 2.553797751s
Without XOR time: 2.600210435s
Useless XOR time: 2.561110200s
Without XOR time: 2.602932919s

$ sudo nice -n -15 java UnsignedLong 
Useless XOR time: 2.578134611s
Without XOR time: 2.490755235s
Useless XOR time: 2.663887447s
Without XOR time: 2.318469412s
Useless XOR time: 2.697392012s
Without XOR time: 2.318214773s
Useless XOR time: 2.591264737s
Without XOR time: 2.319040370s

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: openjdk-6-jre 6b20-1.9.2-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.35-23.41-generic 2.6.35.7
Uname: Linux 2.6.35-23-generic i686
Architecture: i386
Date: Sat Dec 11 14:46:41 2010
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
ProcEnviron:
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: openjdk-6

** Affects: openjdk-6 (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: apport-bug i386 maverick

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which is subscribed to openjdk-6 in ubuntu.
https://bugs.launchpad.net/bugs/689041

Title:
  openjdk-6-jre: java -server performance bug

Status in “openjdk-6” package in Ubuntu:
  New

Bug description:
  When running the attached Java program using the client VM, `(a < 0L)` is evaluated much more quickly than `(a < Long.MIN_VALUE) ^ (a < 0L)`, which is what should happen.

However, using the server VM, `(a < 0L)` evaluates slightly *slower* than `(a < Long.MIN_VALUE) ^ (a < 0L)`.

$ sudo nice -n -15 java -server UnsignedLong 
Useless XOR time: 2.121191887s
Without XOR time: 2.708230708s
Useless XOR time: 2.552766027s
Without XOR time: 2.601783612s
Useless XOR time: 2.553797751s
Without XOR time: 2.600210435s
Useless XOR time: 2.561110200s
Without XOR time: 2.602932919s

$ sudo nice -n -15 java UnsignedLong 
Useless XOR time: 2.578134611s
Without XOR time: 2.490755235s
Useless XOR time: 2.663887447s
Without XOR time: 2.318469412s
Useless XOR time: 2.697392012s
Without XOR time: 2.318214773s
Useless XOR time: 2.591264737s
Without XOR time: 2.319040370s

ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: openjdk-6-jre 6b20-1.9.2-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.35-23.41-generic 2.6.35.7
Uname: Linux 2.6.35-23-generic i686
Architecture: i386
Date: Sat Dec 11 14:46:41 2010
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
ProcEnviron:
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: openjdk-6