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Re: Types with power-of-two size in ggc-page.c extra_order_size_table[]
> On Wed, Sep 16, 2009 at 12:39 AM, Oliver Kellogg
> <oliver.kellogg@t-online.de> wrote:
> > Hi,
> >
> > Looking at ggc-page.c:175ff.,
> >
> > static const size_t extra_order_size_table[] = {
> > ?sizeof (struct var_ann_d),
> > ?sizeof (struct tree_decl_non_common),
> > ?sizeof (struct tree_field_decl),
> > ?sizeof (struct tree_parm_decl),
> > ?sizeof (struct tree_var_decl),
> > ?sizeof (struct tree_list),
> > ?sizeof (struct tree_ssa_name),
> > ?sizeof (struct function),
> > ?sizeof (struct basic_block_def),
> > ?sizeof (bitmap_element),
> > ?sizeof (bitmap_head),
> > ?TREE_EXP_SIZE (2),
> > ?RTL_SIZE (2), ? ? ? ? ? ? ? ? /* MEM, PLUS, etc. ?*/
> > ?RTL_SIZE (9), ? ? ? ? ? ? ? ? /* INSN */
> > };
> >
> > On my openSuSE-11.1 i686-pc-linux-gnu, sizeof (struct basic_block_def)
> > is 64 and sizeof (bitmap_head) is 16.
> > Why are these types entered into extra_order_size_table?
>
> They likely changed in size and/or the 64bit host-wide-int variants are not
> power-of-two sized.
If I remember right, I originally added those based on exploring the
memory report dumps looking for types causing largest overhead. So these
definitly wasn't power of two at that time. We might try to re-do the
tunning by simply removing these and then compiling larger testcase with
-fmem-report and adding those with largest overhead. But this would
have to be done both on 32bit and 64bit host at least.
Honza