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8001028: Improve GC option handling Summary: If there are not enough native resources to create the ReferenceHandler or Finalizer Java threads, the VM will attempt to throw an OOME before the java.lang.Class class has been initialized. This can result in assertion failures and other crashes. Move the initialization of the java.lang.Class class to just before the initialization of the java.lang.ref.Finalizer class. Reviewed-by: jwilhelm, dholmes, coleenp
author johnc
date Wed, 12 Dec 2012 12:07:32 -0800
parents bd7a7ce2e264
children
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<html>
<head>
<title>
C2 Replay
</title>
</head>
<body>

<h1>C2 compiler replay</h1>
<p>
The C2 compiler replay is a function to repeat the compiling process from a crashed java process in compiled method<br>
This function only exists in debug version of VM
</p>
<h2>Usage</h2>
<pre> 
First, use SA to attach to the core file, if suceeded, do
       clhsdb>dumpreplaydata <address> | -a | <thread_id> [> replay.txt]
       create file replay.txt, address is address of Method, or nmethod(CodeBlob)
       clhsdb>buildreplayjars [all | boot | app]
       create files:
         all:
           app.jar, boot.jar
         boot:
           boot.jar
         app:
           app.jar
       exit SA now.
Second, use the obtained replay text file, replay.txt and jar files, app.jar and boot.jar, using debug version of java
       java -Xbootclasspath/p:boot.jar -cp app.jar -XX:ReplayDataFile=<datafile> -XX:+ReplayCompiles ....
       This will replay the compiling process.

       With ReplayCompiles, the replay will recompile all the methods in app.jar, and in boot.jar to emulate the process in java app.

notes:
       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.
       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>

       Use this tool to dump VM type library:
       vmstructsdump libjvm.so > <type_name>.db

       set env SA_TYPEDB=<type_name>.db (refer different shell for set envs)