Re: need to focus on java performance?

[David Daney <ddaney at avtrex dot com>]

Andrew Haley wrote:
> David Daney writes:
>  > Bryce McKinlay wrote:
>  > > David Daney wrote:
>  > >> The calling method's address is in the standard location (as 
>  > >> specified by the ABI), we know how to find the class given this 
>  > >> information. 
>  > >
>  > > Finding the method's address is easy enough, but what about the 
>  > > address of the atable entry containing the pointer to the method?
>  > Isn't the atable part the the calling method's class?  The stack trace 
>  > infrastructure allows you to find the class of a method given an IP that 
>  > is contained by the method.
>
> Mmm, but it's quite expensive.  It would be nice not to do unwinding
> in the class initialization path.

If you structured the little trampoline code properly, you would not 
have to use the full DWARF unwinder.  You only have to go back one 
level.  GCC even has a built-in that allows you to do this 
(__builtin_return_address(0)).  Now looking up the class given this 
might still be slow, but you don't need a complete stacktrace.

David Daney.