Re: [graphds.h] Allocate graph from obstack

[Dimitrios Apostolou <jimis at gmx dot net>]

Hi Paolo,

On Mon, 20 Aug 2012, Paolo Bonzini wrote:
> Il 19/08/2012 18:55, Richard Guenther ha scritto:
> > > > Initially I had one obstack per struct graph, which was better than using
> > > > XNEW for every edge, but still obstack_init() called from new_graph() was
> > > > too frequent.
> > > >
> > > > So in this iteration of the patch the obstack is static global, initialised
> > > > once and never freed. Please advise on whether this is acceptable, and also
> > > > where I should initialise the obstack once, and avoid checking if it's NULL
> > > > in every use.
> > > >
> > > > Minor speed gains (couple of ms), tested with pre-C++ conversion snapshot,
> > > > I'll retest soon and post update.
> > Either an obstack per graph or the ability to specify an obstack for allocation.
> > A global obstack with global lifetime is bad IMHO.
>
> Dimitrios's patch has a per-file obstack with per-pass lifetime

Notice that I never call XOBDELETE with NULL argument, I only free the 
first object, which means that the 4KB per obstack overhead is retained 
until program exit, I did that to save on malloc calls.


Thanks,
Dimitris