Re: [rvm-research] Hi Robin, Sorry to bother you again.

[Robin G. <rob...@an...>]

Xinwei,

You are asking several questions here.  The one I'm answering is this:

>  I want to know which thread execute "invokespecial" bytecode 
currently, how can I know that?
As far as I understand your question, what you're asking is: "If you 
look at the system at a certain instant (eg via a timer), which threads 
are currently executing an invokespecial bytecode at some point in their 
call stack".

As far as I can see, what you need to do to answer this question is:
- Halt all the threads
- Work through the stack of each thread, looking for invokespecial 
bytecodes currently in flight

if you apply what I said below at this point, then the problem is solved.

Regards,
Robin

Xinwei Xie wrote:
> Hi Robin,
> Thanks for reply.
> What I mean is specified to another poster. Please check it out ;-)
> http://www.nabble.com/-rvm-research--Can-someone-explain-it-to-me--tt21490704.html
>
> Regards,
> Xinwei
>
>
> Robin Garner wrote:
>   
>> Hi Xinwei,
>>
>> So do you mean that you want to be able to freeze the system, examine 
>> all executing threads, and identify which ones are currently executing 
>> an 'invokespecial' ?
>>
>> If you examine the method
>>
>>   org.jikesrvm.scheduler.Scheduler#dumpStack(Address ip, Address fp)
>>
>> take a look at the code starting at line 743,
>>     // normal java frame(s)
>>     CompiledMethod compiledMethod = 
>> CompiledMethods.getCompiledMethod(compiledMethodId);
>>     if (compiledMethod == null) {
>>       showMethod(compiledMethodId, fp);
>>     } else if (compiledMethod.getCompilerType() == CompiledMethod.TRAP) {
>>       showMethod("hardware trap", fp);
>>     } else {
>>       RVMMethod method = compiledMethod.getMethod();
>>       Offset instructionOffset = compiledMethod.getInstructionOffset(ip, 
>> false);
>>       int lineNumber = 
>> compiledMethod.findLineNumberForInstruction(instructionOffset);
>>
>> you can see how to locate the instruction from the call stack. 
>>
>> If you look at the findLineNumberForInstruction method of a 
>> CompiledMethod, you should see how you could write a method that would 
>> return the bytecode for the instruction rather than the line number.
>>
>> cheers,
>> Robin
>>
>> Xinwei Xie wrote:
>>     
>>> Hi Steve,
>>>
>>> Thanks for your kind reply. :-)
>>>
>>> I've checked out the bootstrap process. What I mean is when eveything is
>>> ready, i.e., the virtual machine machine is fully booted, is the compiler
>>> going to compile every bytecode into native code and execute them? My
>>> question is where can it be started? Is there some entry point in
>>> JikesRVM
>>> that can execute the code? e.g., I want to know which thread execute
>>> "invokespecial" bytecode currently, how can I know that? Hopefully I
>>> explain
>>> it clearly.
>>>
>>> Regards,
>>> Xinwei
>>>
>>> Steve Blackburn wrote:
>>>   
>>>       
>>>> On 15/01/2009, at 3:33 PM, Xinwei Xie wrote:
>>>>     
>>>>         
>>>>> You mean jikesrvm will execute native codes.
>>>>>       
>>>>>           
>>>> No.  Eliot meant that Jikes RVM will execute bytecode "natively".
>>>>
>>>> "Native code" usually refers to C code etc.  Jikes RVM, can of course  
>>>> do that too.  But Eliot was pointing out that bytecodes are not  
>>>> interpreted, but rather, they are compiled to machine code which is  
>>>> then executed directly (not interpreted).
>>>>
>>>>     
>>>>         
>>>>> However, where is the execution
>>>>> entrypoint? I am always trying to find it out. ;-)
>>>>>       
>>>>>           
>>>> Do you mean how is the JVM bootstrapped?
>>>>
>>>> It starts with a small piece of C & asm, which you can look at in  
>>>> tools/bootImageRunner/ia32/libVM.c  and the createVM() function.    
>>>> Among other things, this mmaps the boot iamge and throws execution to  
>>>> code that you can find in org.jikesrvm.VM.java
>>>>
>>>> Cheers,
>>>>
>>>> --Steve
>>>>
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>>>>
>>>>     
>>>>         
>>> -----
>>> Xinwei Xie
>>> School of Computer Science and Engineering
>>> University of New South Wales
>>> Sydney, Australia
>>>   
>>>       
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>>     
>
>
> -----
> Xinwei Xie
> School of Computer Science and Engineering
> University of New South Wales
> Sydney, Australia
>