On Fri, Apr 24, 2015 at 12:49:05PM -0700, Andrew Morton wrote:
> On Thu, 23 Apr 2015 23:40:01 +0200 Hagen Paul Pfeifer <ha...@jauu.net> wrote:
>
> > GCC inlining heuristics are sometimes quizzical. Especially with inline
> > assembler constructs GCC seems to have issues. A allyesconfig show a rather
> > long list of functions where GCC inlining decisions are questionable (not
> > inlined).
>
> I can't reproduce this with either gcc-4.8.2 or gcc-4.4.4. The patch
> makes zero difference to `size vmlinux' and a bit of poking around with
> nm doesn't show any out-of-lined versions of the functions you
> identify.
>
> So. More details, please. How to demonstrate this, gcc versions, etc.
>
> > Furthermore, because the functions are declared with static
> > linkage each function is copied n times - and n can be rather high:
> >
> > atomic_inc: 544 duplicates
> > rcu_read_unlock: 453 duplicates
> > rcu_read_lock: 383 duplicates
Hmmm... allyesconfig would have PROVE_RCU=y, which would mean that the
above two would contain lockdep calls that might in some cases defeat
inlining. With the more typical production choice of PROVE_RCU=n, I would
expect these to just be a call instruction, which should get inlined.
Thanx, Paul
> > get_dma_ops: 271 duplicates
> > arch_local_irq_restore: 258 duplicates
> > atomic_dec: 215 duplicates
> > kzalloc: 185 duplicates
> > cpumask_check: 157 duplicates
> > test_and_set_bit: 156 duplicates
> > cpumask_next: 146 duplicates
> > list_del: 131 duplicates
> > kref_get: 126 duplicates
>
> That's pretty pathetic.
>
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