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

[Daniel Jacobowitz <drow at false dot org>]

On Thu, Feb 26, 2004 at 05:22:21PM -0500, Elena Zannoni wrote:
> Jim Blandy writes:
>  > 
>  > 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.
> 
> Jim, there was agreement to not touch these central files until after
> the branch.

Was there?  The closest I saw was an agreement not to merge intercu
support.  This patch is not particularly important, or the other
optimization patch, but they are independent of that.  I would like to
see the duplicate symbols patch reviewed before the branch.

In any case, I won't commit this one until after the branch - which I
think is coming up in about an hour.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer