Compiler Configuration on JVM
The options for configuring the Graal compiler on the JVM are in 3 categories.
General Options
These are general options for setting/getting configuration details.
-XX:-UseJVMCICompiler
: This disables use of the Graal compiler as the top tier JIT. This is useful when wanting to compare performance of the Graal compiler against the native JIT compilers.-
-Dgraal.CompilerConfiguration=<name>
: Selects the Graal compiler configuration to use. If omitted, the compiler configuration with the highest auto-selection priority is used. To see the set of available configurations, supply the value help to this option.The current configurations and their semantics are:
enterprise
: To produce highly optimized code with a possible trade-off to compilation time. [GraalVM Enterprise]community
: To produce reasonably optimized code with a faster compilation time.economy
: To compile as fast as possible with less optimal throughput of the generated code.
-
-Dgraal.ShowConfiguration=none
: Prints information about the Graal compiler configuration selected. This option only produces output when the compiler is initialized. By default, the Graal compiler is initialized on the first top-tier compilation. For this reason, the way to use this option is as follows:java -XX:+EagerJVMCI -Dgraal.ShowConfiguration=info -version
.The accepted values for this option are:
none
: To show no information.info
: To print one line of output showing the name of the compiler configuration in use and the location it is loaded from.verbose
: To print detailed compiler configuration information.
-
-Dgraal.MitigateSpeculativeExecutionAttacks=None
: Selects a strategy to mitigate speculative execution attacks (e.g., SPECTRE).Accepted values are:
None
: No mitigations are used in JIT compiled code.AllTargets
: All branches are protected against speculative attacks. This has a large performance impact.GuardTargets
: Only branches that preserve Java memory safety are protected. This has reduced performance impact.NonDeoptGuardTargets
: Same as GuardTargets except that branches which deoptimize are not protected since they can not be executed repeatedly.
Performance Tuning Options
-Dgraal.UsePriorityInlining=true
: This can be used to disable use of the advanced inlining algorithm that favours throughput over compilation speed. [GraalVM Enterprise]-Dgraal.Vectorization=true
: This can be used to disable the auto vectorization optimization. [GraalVM Enterprise]-Dgraal.OptDuplication=true
: This can be used to disable the path duplication optimization. [GraalVM Enterprise]-Dgraal.TuneInlinerExploration=0
: This can be used to try tune for better peak performance or faster warmup. It automatically adjusts values governing the effort spent during inlining. The value of the option is a float clamped between-1
and1
inclusive. Anything below0
reduces inlining effort and anything above0
increases inlining effort. In general, peak performance is improved with more inlining effort while less inlining effort improves warmup (albeit to a lower peak). Note that this option is only a heuristic and the optimal value can differ from application to application. [GraalVM Enterprise]-
-Dgraal.TraceInlining=false
: Enables tracing of inlining decisions. This can be used for advanced tuning where it may be possible to change the source code of the program. The output format is shown below:compilation of 'Signature of the compilation root method': at 'Sig of the root method' ['Bytecode index']: <'Phase'> 'Child method signature': 'Decision made about this callsite' at 'Signature of the child method' ['Bytecode index']: |--<'Phase 1'> 'Grandchild method signature': 'First decision made about this callsite' \--<'Phase 2'> 'Grandchild method signature': 'Second decision made about this callsite' at 'Signature of the child method' ['Bytecode index']: <'Phase'> 'Another grandchild method signature': 'The only decision made about this callsite.'
For example:
compilation of java.lang.Character.toUpperCaseEx(int): at java.lang.Character.toUpperCaseEx(Character.java:7138) [bci: 22]: ├──<GraphBuilderPhase> java.lang.CharacterData.of(int): no, bytecode parser did not replace invoke └──<PriorityInliningPhase> java.lang.CharacterData.of(int): yes, worth inlining according to the cost-benefit analysis. at java.lang.Character.toUpperCaseEx(Character.java:7138) [bci: 26]: ├──<GraphBuilderPhase> java.lang.CharacterDataLatin1.toUpperCaseEx(int): no, bytecode parser did not replace invoke └──<PriorityInliningPhase> java.lang.CharacterDataLatin1.toUpperCaseEx(int): yes, worth inlining according to the cost-benefit analysis. at java.lang.CharacterDataLatin1.toUpperCaseEx(CharacterDataLatin1.java:223) [bci: 4]: ├──<GraphBuilderPhase> java.lang.CharacterDataLatin1.getProperties(int): no, bytecode parser did not replace invoke └──<PriorityInliningPhase> java.lang.CharacterDataLatin1.getProperties(int): yes, worth inlining according to the cost-benefit analysis.
Diagnostic Options
-
-Dgraal.CompilationFailureAction=Silent
: Specifies the action to take when compilation fails by throwing an exception.The accepted values are:
Silent
: Print nothing to the console.Print
: Print a stack trace to the console.Diagnose
: Retry the compilation with extra diagnostics enabled. On VM exit, the collected diagnostics are saved to a zip file that can be submitted along with a bug report. A message is printed to the console describing where the diagnostics file is saved:Graal diagnostic output saved in /Users/graal/graal_dumps/1549459528316/graal_diagnostics_22774.zip
ExitVM
: Same asDiagnose
except that the VM process exits after retrying.
For all values except for
ExitVM
, the VM continues executing. -Dgraal.CompilationBailoutAsFailure=false
: The compiler may not complete compilation of a method due to some property or code shape in the method (e.g., exotic uses of the jsr and ret bytecodes). In this case the compilation bails out. If you want to be informed of such bailouts, this option makes GraalVM treat bailouts as failures and thus be subject to the action specified by the-Dgraal.CompilationFailureAction
option.-Dgraal.PrintCompilation=false
: Prints an informational line to the console for each completed compilation. For example:HotSpotCompilation-11 Ljava/lang/Object; wait ()V | 591ms 12B 92B 4371kB HotSpotCompilation-175 Ljava/lang/String; lastIndexOf (II)I | 590ms 126B 309B 4076kB HotSpotCompilation-184 Ljava/util/concurrent/ConcurrentHashMap; setTabAt ([Ljava/util/concurrent/ConcurrentHashMap$Node;ILjava/util/concurrent/ConcurrentHashMap$Node;)V | 591ms 38B 67B 3411kB HotSpotCompilation-136 Lsun/nio/cs/UTF_8$Encoder; encode ([CII[B)I | 591ms 740B 418B 4921
Setting Compiler Options with Language Launchers
The Graal compiler properties above are usable with some other GraalVM launchers such as
node
, js
and lli
. The prefix for specifying the properties is slightly different.
For example:
java -XX:+EagerJVMCI -Dgraal.ShowConfiguration=info -version
Becomes:
js --jvm --vm.Dgraal.ShowConfiguration=info -version
Note the
-D
prefix is replaced by--vm.D
.