Re: Perf support for interpreted and Just-In-Time translated olanguages

[Andi Kleen <andi@firstfloor.org>]

> This may be more complex then needed.  We really just need to track the
> symbol.  From talking with the Java experts, they say the reused memory
> is almost always from methods that are loaded/used early when
> initializing the program.  Then the memory gets reused by a method that
> runs for the bulk of the time.  So by getting a timestamp for when the
> symbol was loaded you can then determine the length of time each symbol
> was in the anonymous memory.  Then just associate the sample with the
> symbol that was present in the anonymous memory the longest.  You can
> also tag the symbol names to say that they reside in the same memory,
> ie, the memory was reused. To warn the user that there maybe some
> ambiguity in the sample to symbol association.  

We need a way to transfer the code too. Just symbols is not enough.
This needs exact tracking.

> The source file and line number information is optionally available from
> the jvm via the jvmti complied method load callback.  With this
> information on the symbol, line number and source file, perf could then
> persist the data in an ELF formatted file. 

I'm not sure ELF/dwarf is the right way to go there. That would be very
complex. 

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.