Re: [RFA/commit/dwarf] Create partial symbols for nested subprograms

[Daniel Jacobowitz <drow@false.org>]

On Thu, Sep 11, 2008 at 10:54:22AM -0700, Joel Brobecker wrote:
> > Do you have any performance data for GDB startup with this change?
> 
> I am not sure I am doing the right kind of performance test, so if you
> have some better suggestions, please let me know. For now, here is what
> I did:
> 
>   . I used one of the large Ada applications we have:
>     It is 290MB in size - reduced to 160MB when I strip the debugging
>     info => the debugging info size is roughly 130MB.
>     The number of real lines of code is 700K spread in ~3500 files,
>     and it has a total of 39,000 subprograms declared in the debugging
>     info.
> 
>   . To measure the startup time, I used the --statistics command-line
>     switch.

I usually use 'gdb -batch foo.exe' to time reading partial symbols,
and 'gdb -readnow -batch foo.exe' to time full symbols (only partial
symbols are at issue here).

> It looks like roughly a 4% increase in startup time. Not sure whether
> that's considered a large increase or not - I just think that it's not
> noticeable. None of our users have reported issues with startup time.

Your users must be more patient than mine or Tom's :-)  I consider
startup time to be pretty important, and I've been working on bringing
it down... Tom's been working on an even more drastic version.

> But, to make sure that only languages that have this feature get hit,
> I adjusted the patch to only search nested procedure when the language
> allows them.

Does it work / help to do the check here too:

>  	  && (load_all
>  	      || last_die->tag == DW_TAG_namespace
>  	      || last_die->tag == DW_TAG_enumeration_type
> +	      || last_die->tag == DW_TAG_subprogram
> +	      || last_die->tag == DW_TAG_lexical_block
>  	      || (cu->language != language_c
>  		  && (last_die->tag == DW_TAG_class_type
>  		      || last_die->tag == DW_TAG_interface_type

That'll bring the memory usage back down for non-Ada.

-- 
Daniel Jacobowitz
CodeSourcery