Re: [RFA/dwarf] Allocate abbrevs from a new obstack

[Daniel Jacobowitz <drow@false.org>]

On Thu, Feb 26, 2004 at 05:09:36PM -0500, Jim Blandy wrote:
> 
> Daniel Jacobowitz <drow@false.org> writes:
> > Another independent performance optimization from my profiling.  This one is
> > good for several percent speedup on mainline.  My original description:
> > 
> >   - It plugs a huge memory leak.  After loading partial symbols for
> >   libc, GDB uses 5.6MB memory without this patch and 1.6MB with it.
> >   We weren't emptying the abbrev table.
> > 
> > [Specifically, we were emptying it after dwarf2_build_psymtabs_hard,
> > instead of once each time through the loop.  dwarf2_read_abbrevs then
> > zeroed out the allocated, unreferenced pointers.]
> > 
> >   - I spent a lot of time trying to find alternate data structures that
> >   would be more efficient.  The expandable hash table is slower, even if
> >   you initially allocate it to the right size.  The splay tree I expected
> >   to be quite good in this case, but it isn't either; the overhead is simply
> >   too high.  The fixed-size ad-hoc hash table appears to be the best we can
> >   do.
> > 
> > Tested on i686-pc-linux-gnu, no regressions.  OK to commit?
> 
> Looks great --- please do.

OK, I've retested this and checked it in.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer