Re: Re: Re: Calculating Methods' Local Variable Sizes at Runtime

You need to implement it, like Eugene said.

Do a traversal of the object tree and sum up the sizes. It's expensive,
which is why this methods isn't commonly used for memory accounting.

See http://portal.acm.org/citation.cfm?id=1029888 and the papers it
references for more background.

 - Godmar

On Mon, Mar 29, 2010 at 6:23 PM, Nemo Caviani <[email protected]>wrote:

> Thanks Eugene for the reply.
>
> yes, using visitLocalVariable I am able to identify the set of parameters
> passed to a method. What I can't figure out is how to get the actual values
> for these parameters off the stack to calculate their real sizes. I can
> figure out their names and their types from the method signature, and for
> the primitive types a lookup table can give me the size of their memory
> usage. What I don't know, is how to get the actual size of non-primitive
> parameters. If the nonprimitive type contains an array or a list, the length
> of the array or the list also size becomes a critical factor in figuring out
> the amount of space it uses.
>
> so if you or anyone in the list can give me a clue on how to access the
> actual value of a parameter from the local stack and calculate its size,
> that would be a great help to me indeed.
>
> thanks a lot,
> Nemo
>
> On Mon, Mar 29, 2010 at 5:42 AM, Eugene Kuleshov <[email protected]>wrote:
>
>>
>>  So you want to calculate something at runtime before method call and
>> after the method call. For your scenario, primitive types are obvious and
>> for a non-primitive types the easiest would be to write a static helper
>> method, which you call for every parameter and non-primitive method return
>> value. All param and return types you can retrieve from the called method
>> signature and then generate code to call your static method. You may have to
>> create some temporary variables in order to get the parameter values off the
>> stack, but your transformation sould not change state of the stack at the
>> point original method is called.
>>
>>  Hope that helps.
>>
>>  regards,
>>  Eugene
>>
>>
>>
>> Nemo Caviani wrote:
>>
>>> Hello All,
>>>
>>> I am a newbie to ASM and I would appreciate your help with the following
>>> matter.
>>> I have load-time instrumented my bytecode. I keep all sorts of
>>> information for my classes and methods to measure CPU time, memory usage,
>>> etc. Now, what I need to do is to calculate the actual amount of data that
>>> is passed from one method to another through the input parameters and also
>>> its return value of the method.
>>>
>>> This is in particular important for me as it enables me to measure the
>>> actual amount of data that arrays and link lists take when they are passed
>>> as arguments to a method or when they are returned from methods.
>>>
>>> I have checked the visitLocalVariable method, but I am not sure how I can
>>> relate the name and the description of a local variable to its actual data
>>> size in the local stack memory, especially when it is not a basic type like
>>> INT or BOOLEAN.
>>>
>>> I also looked into visitFrame which seems to have more details about the
>>> variables of a method. However, overwriting visitFrame results in a
>>> VerifyError as it seems like I need to calculate the stack size for the
>>> method manually, which I don't know how.
>>>
>>> I highly appreciate any help from you guys.
>>>
>>> thanks a lot,
>>> Nemo
>>>
>>
>>
>>
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>
>
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