Re: [rfa/dwarf] Support for attributes pointing to a different CU

[Daniel Jacobowitz <drow@false.org>]

On Mon, Oct 04, 2004 at 04:14:24PM -0500, Jim Blandy wrote:
> 
> Daniel Jacobowitz <drow@false.org> writes:
> > On Wed, Sep 29, 2004 at 12:49:35PM -0500, Jim Blandy wrote:
> > > Since we never toss types anyway, would it make sense to move
> > > type_hash to dwarf2_per_objfile?
> > 
> > I don't think so.  type_hash is used in two ways: individual items are
> > set, when we know which CU we ought to have, and a whole CU is
> > restored, when we know which CU we're restoring.  It's always more
> > efficient to have a lot of small hash tables if you know precisely
> > which one you'll need; fewer collisions.
> 
> Really?  libiberty/hashtab.c is a resizing hash table; I thought hash
> table resizing was supposed to keep the collision rate roughly
> constant (modulo hysteresis) regardless of the number of elements.  If
> that's not so, doesn't that mean your hash function isn't doing its
> job spreading the elements across the (adequately sized) table?

Poor job of thinking on my part, there.  The rest of the paragraph
still makes sense to me, though.  For instance, in a resizing hash
table, I suspect that there is more copying to have one large
expandable hash table than several small ones.

I haven't done the math for that, of course.  Maybe I've got it
backwards.  Do you think there would be any advantage to doing it the
other way round?

-- 
Daniel Jacobowitz