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1 <html> |
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2 <head> |
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3 <title> |
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4 C2 Replay |
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5 </title> |
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6 </head> |
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7 <body> |
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8 |
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9 <h1>C2 compiler replay</h1> |
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10 <p> |
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11 The C2 compiler replay is a function to repeat the compiling process from a crashed java process in compiled method<br> |
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12 This function only exists in debug version of VM |
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13 </p> |
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14 <h2>Usage</h2> |
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15 <pre> |
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16 First, use SA to attach to the core file, if suceeded, do |
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17 clhsdb>dumpreplaydata <address> | -a | <thread_id> [> replay.txt] |
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18 create file replay.txt, address is address of Method, or nmethod(CodeBlob) |
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19 clhsdb>buildreplayjars [all | boot | app] |
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20 create files: |
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21 all: |
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22 app.jar, boot.jar |
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23 boot: |
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24 boot.jar |
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25 app: |
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26 app.jar |
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27 exit SA now. |
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28 Second, use the obtained replay text file, replay.txt and jar files, app.jar and boot.jar, using debug version of java |
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29 java -Xbootclasspath/p:boot.jar -cp app.jar -XX:ReplayDataFile=<datafile> -XX:+ReplayCompiles .... |
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30 This will replay the compiling process. |
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31 |
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32 With ReplayCompiles, the replay will recompile all the methods in app.jar, and in boot.jar to emulate the process in java app. |
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33 |
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34 notes: |
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35 1) Most time, we don't need the boot.jar which is the classes loaded from JDK. It will be only modified when an agent(JVMDI) is running and modifies the classes. |
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36 2) If encounter error as "<flag>" not found, that means the SA is using a VMStructs which is different from the one with corefile. In this case, SA has a utility tool vmstructsdump which is located at agent/src/os/<os>/proc/<os_platform> |
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37 |
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38 Use this tool to dump VM type library: |
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39 vmstructsdump libjvm.so > <type_name>.db |
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40 |
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41 set env SA_TYPEDB=<type_name>.db (refer different shell for set envs) |
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