Re: [patch] uninline init_waitqueue_*() functions

Andrew Morton
2006-07-05T20:14:54Z

Ingo Molnar <mingo@elte.hu> wrote:
>
> > > i also tried a config with the best size settings (disabling
> > > FRAME_POINTER, enabling CC_OPTIMIZE_FOR_SIZE), and this gives:
> > >
> > > text data bss dec filename
> > > 20777768 6076042 3081864 29935674 vmlinux.x32.size.before
> > > 20748140 6076178 3081864 29906182 vmlinux.x32.size.after
> > >
> > > or a 34.8 bytes win per callsite (29K total).
> > >
> >
> > With gcc-4.1.0 on i686, uninlining those three functions as per the
> > below patch _increases_ the allnoconfig vmlinux's .text from 833456
> > bytes to 833728.
>
> that's just the effect of CONFIG_REGPARM and CONFIG_CC_OPTIMIZE_FOR_SIZE
> not being set in an allnoconfig. Once i set them the text size evens
> out:
>
> 431348 60666 27276 519290 7ec7a vmlinux.x32.mini.before
> 431359 60666 27276 519301 7ec85 vmlinux.x32.mini.after
>
> compiling without CONFIG_REGPARM on i686 (if you care about text size)
> makes little sense. It penalizes function calls artificially.

OK, but what happened to the 35-bytes-per-callsite saving?

Sorry to keep going on about this, but your numbers seem just too big to
me, and the above confirms that, and I don't know what's happening.

It doesn't seem right that uninlining something like this:

static inline void init_waitqueue_func_entry(wait_queue_t *q,
wait_queue_func_t func)
{
q->flags = 0;
q->private = NULL;
q->func = func;
}

is going to gain us much code size benefit at all. Let alone
runtime/codegen benefit.