| <html> |
| <head> |
| <title> |
| Replay |
| </title> |
| </head> |
| <body> |
| |
| <h1>Compiler replay</h1> |
| <p> |
| The 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 succeeded, do |
| hsdb> dumpreplaydata <address> | -a | <thread_id> [> replay.txt] |
| create file replay.txt, address is address of Method, or nmethod(CodeBlob) |
| hsdb> 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) |
