Re: [PATCH v6 19/29] memcg: infrastructure to match an allocation to the right cache

Michal Hocko
2012-11-06T08:04:08Z

On Mon 05-11-12 16:28:37, Andrew Morton wrote:
> On Thu, 1 Nov 2012 16:07:35 +0400
> Glauber Costa <glommer@parallels.com> wrote:
>
> > +static __always_inline struct kmem_cache *
> > +memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
>
> I still don't understand why this code uses __always_inline so much.

AFAIU, __always_inline (resp. __attribute__((always_inline))) is the
same thing as inline if optimizations are enabled
(http://ohse.de/uwe/articles/gcc-attributes.html#func-always_inline).
Which is the case for the kernel. I was always wondering why we have
this __always_inline thingy.
It has been introduced back in 2004 by Andi but the commit log doesn't
say much:
"
[PATCH] gcc-3.5 fixes

Trivial gcc-3.5 build fixes.
"
Andi what was the original motivation for this attribute?

> I don't recall seeing the compiler producing out-of-line versions of
> "static inline" functions

and if it decides then __always_inline will not help, right?

--
Michal Hocko
SUSE Labs