Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers

Ingo Molnar
2005-12-29T07:59:53Z

* Adrian Bunk <bunk@stusta.de> wrote:

> > unit-at-a-time still increases the kernel stack footprint somewhat (by
> > about 5% in the CC_OPTIMIZE_FOR_SIZE case), but not by the insane degree
> > gcc3 used to, which prompted the original -fno-unit-at-a-time addition.
> >...
>
> Please hold off this patch.
>
> I do already plan to look at this after the smoke has cleared after
> the 4k stacks issue. I want to avoid two different knobs both with
> negative effects on stack usage (currently CONFIG_4KSTACKS=y, and
> after your patch gcc >= 4.0) giving a low testing coverage of the
> worst cases.

this is obviously not 2.6.15 stuff, so we've got enough time to see the
effects. [ And what does "I do plan to look at this" mean? When
precisely, and can i thus go to other topics without the issue being
dropped on the floor indefinitely? ]

also note that the inlining patch actually _reduces_ average stack
footprint by ~3-4%:
orig +inlining
# of functions above 256 bytes: 683 660
total stackspace, bytes: 148492 142884

it is the unit-at-a-time patch that increases stack footprint (by about
7-8%, which together with the inlining patch gives a net ~5%).

Ingo