Example
Monitoring Mode
1
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devkit diag jvm-jitter -a monitor -e jit.deoptimization -c /home/DevKit-CLI-xx.xx.xx-Linux-Kunpeng/diag/config/kunpeng_devkit.cfg -p 1179 |
- The -a monitor parameter specifies the monitoring mode, the -e jit.deoptimization parameter specifies de-optimization event monitoring, the -c parameter specifies the configuration file path, and the -p 1179 parameter specifies the ID of the Java process to be detected. The current working directory is /home/test/workspace/demo.
- To enable monitoring, set the <enabled> option of the <jvm.DeoptimizationStatistics> parameter in the kunpeng_devkit.cfg file to true, and set the MONITOR_JIT option in the devkit_odin.properties file in the working directory to true. Set other parameters based on your requirements. In this example, <duration> is set to 30 s and <jitTraceThreshold> is set to 0.5.
Command output:
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2025-04-11 15:18:29,173 INFO [jvm-diagnosis-guardian-common-thread-1] c.h.k.devkit.odin.cli.CliWorker: UNIX socket connection established successfully. 2025-04-11 15:18:29,287 INFO [jvm-diagnosis-profiler-wireIo-thread-1] c.h.k.devkit.odin.cli.CliWorker: other type: CPU_JDBC_METHOD 2025-04-11 15:18:30,968 INFO [jvm-diagnosis-profiler-wireIo-thread-1] c.h.k.devkit.odin.cli.CliWorker: other type: NONE 2025-04-11 15:18:32,000 INFO [jvm-diagnosis-profiler-wireIo-thread-1] c.h.k.devkit.odin.cli.CliWorker: JVM_JIT_MONITOR: deoptimizationRatio=0.0, startTime=2025/04/11 PM 03:18:31.925, compileCount=2027, deoptimizationCount=30 2025-04-11 15:18:32,955 INFO [jvm-diagnosis-profiler-wireIo-thread-1] c.h.k.devkit.odin.cli.CliWorker: JVM_JIT_MONITOR: deoptimizationRatio=5.0, startTime=2025/04/11 PM 03:18:32.925, compileCount=2241, deoptimizationCount=35 2025-04-11 15:18:33,927 INFO [jvm-diagnosis-profiler-wireIo-thread-1] c.h.k.devkit.odin.cli.CliWorker: JVM_JIT_MONITOR: deoptimizationRatio=0.0, startTime=2025/04/11 PM 03:18:33.925, compileCount=2276, deoptimizationCount=35 2025-04-11 15:18:34,927 INFO [jvm-diagnosis-profiler-wireIo-thread-1] c.h.k.devkit.odin.cli.CliWorker: JVM_JIT_MONITOR: deoptimizationRatio=0.0, startTime=2025/04/11 PM 03:18:34.926, compileCount=2280, deoptimizationCount=35 2025-04-11 15:18:35,927 INFO [jvm-diagnosis-profiler-wireIo-thread-1] c.h.k.devkit.odin.cli.CliWorker: JVM_JIT_MONITOR: deoptimizationRatio=0.0, startTime=2025/04/11 PM 03:18:35.926, compileCount=2288, deoptimizationCount=35 ... ... ... |
Analysis Mode
1
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devkit diag jvm-jitter -a report -e jit.deoptimization -f /home/test/workspace/demo/devkit_odin_jfr/devkit_20250411_152001_944.jfr -o /home/test/data |
The -a report parameter specifies the analysis mode, the -e jit.deoptimization parameter specifies de-optimization analysis, the -f parameter specifies the path to the JFR file to be analyzed, and the -o /home/test/data parameter specifies the path to the generated flame graph file.
Command output:
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-------------------------------------------- Reason Deoptimization methods -------------------------------------------- loop_limit_check 1 unstable_if 10 class_check 12 ------------------------------------------- Action Deoptimization methods ------------------------------------------- maybe_recompile 13 reinterpret 10 ----------------------------------------------------------------------------------------------------------------------------------------- Method Reason Action Instruction Line No. Compiler StartTime ----------------------------------------------------------------------------------------------------------------------------------------- java.io.BufferedReader.readLine(boolean, boolean[]) unstable_if reinterpret if_icmplt 330 c2 2025/04/11 PM 03:20:01.994 java.io.ByteArrayOutputStream.ensureCapacity(int) unstable_if reinterpret ifle 99 c2 2025/04/11 PM 03:20:02.000 java.lang.StringLatin1.canEncode(int) unstable_if reinterpret ifne 54 c2 2025/04/11 PM 03:20:02.009 java.lang.StringBuffer.toString() unstable_if reinterpret ifeq 716 c2 2025/04/11 PM 03:20:02.462 org.json.JSONObject.isDecimalNotation(String) unstable_if reinterpret if_icmpgt 2204 c2 2025/04/11 PM 03:20:02.469 org.json.JSONObject.isDecimalNotation(String) unstable_if reinterpret if_icmpgt 2204 c2 2025/04/11 PM 03:20:02.469 org.json.JSONObject.writeValue(Writer, Object, int, int) unstable_if reinterpret ifeq 2551 c2 2025/04/11 PM 03:20:02.510 org.json.JSONObject.writeValue(Writer, Object, int, int) unstable_if reinterpret ifeq 2551 c2 2025/04/11 PM 03:20:02.867 test02.App.deserializeJson(String) unstable_if reinterpret if_icmpge 66 c2 2025/04/11 PM 03:20:05.149 test02.App.serializeJson(List) unstable_if reinterpret ifeq 93 c2 2025/04/11 PM 03:20:05.401 2025-04-11 15:26:16,419 INFO [main] c.h.k.d.o.c.r.JitDeoptimizationReport: The above methods support disabling method-level branch prediction to eliminate deoptimization. Usage: -XX:CompileCommand=dontprediction,methodName 2025-04-11 15:26:16,620 INFO [main] c.h.k.d.o.cli.report.JfrToFlameGraph: The generated flame graph is: /home/test/data/FlameGraph_devkit_20250411_152001_944_20250411152616.html |
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Parameter |
Description |
|---|---|
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Method |
Name of the method that triggers de-optimization. |
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Reason |
Cause of de-optimization. unstable_if indicates that branch prediction fails. You can set -XX:CompileCommand=dontprediction,methodName to disable method-level branch prediction so that the specified functions do not generate de-optimization of the unstable_if type. |
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Action |
Operation performed by the JVM for de-optimization, for example:
|
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Instruction |
Bytecode instruction that triggers de-optimization. |
|
Line No. |
Line number of the Java source code that triggers de-optimization. |
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Compiler |
Compiler types that involve de-optimization, for example:
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Figure 1 JIT flame graph
Parent topic: JVM Jitter Detector