-XX:[+|-]MergeCompilerOptions
This option enables or disables the merging of multiple -Xjit or -Xaot options into a single -Xjit or -Xaot option.
Syntax
-XX:[+|-]MergeCompilerOptions
| Setting | Effect | Default |
|---|---|---|
-XX:+MergeCompilerOptions |
Enable | |
-XX:-MergeCompilerOptions |
Disable | yes |
Explanation
By default, if you specify -Xjit option (or -Xaot option) multiple times, only the last option takes effect. Therefore, on adding an -Xjit option, the resultant behavior might not be as expected, if any instance of this option already exists. It is time-consuming to find the existing instances and try combining them manually so that the system behaves as required.
You can use the -XX:+MergeCompilerOptions option to merge all the existing instances of the -Xjit options logically. To retain the default behavior, whereby only the last option takes effect, you can use the -XX:-MergeCompilerOptions option.
If both -Xjit and -Xaot options exist and you use the -XX:+MergeCompilerOptions option, then multiple -Xjit options are merged into a single -Xjit option and multiple -Xaot options are merged into a single -Xaot option.
Examples
One -Xjit option
java -Xshareclasses:none -Xjit:version -version
-Xjit option that is applied - version
java -XX:+MergeCompilerOptions -Xshareclasses:none -Xjit:version -version
-Xjit option that is applied - version
java -XX:-MergeCompilerOptions -Xshareclasses:none -Xjit:version -version
-Xjit option that is applied - version
Multiple -Xjit options
java -Xshareclasses:none '-Xjit:verbose={compilePerformance},vlog=vlog' -Xjit:version -version
-Xjit option that is applied - version
java -XX:+MergeCompilerOptions -Xshareclasses:none '-Xjit:verbose={compilePerformance},vlog=vlog' -Xjit:version -version
-Xjit options that are applied - verbose={compilePerformance},vlog=vlog,version
java -XX:-MergeCompilerOptions -Xshareclasses:none '-Xjit:verbose={compilePerformance},vlog=vlog' -Xjit:version -version
-Xjit option that is applied - version
Both -XX:+MergeCompilerOptions and -XX:-MergeCompilerOptions
If there are multiple -XX:[+|-]MergeCompilerOptions options with multiple -Xjit options, the last -XX:[+|-]MergeCompilerOptions setting takes effect before the -Xjit options are processed.
java -XX:+MergeCompilerOptions -XX:-MergeCompilerOptions -Xshareclasses:none '-Xjit:verbose={compilePerformance},vlog=vlog' -Xjit:version -version
-Xjit option that is applied - version
java -XX:-MergeCompilerOptions -XX:+MergeCompilerOptions -Xshareclasses:none '-Xjit:verbose={compilePerformance},vlog=vlog' -Xjit:version -version
-Xjit options that are applied - {compilePerformance},vlog=vlog,version