Re: [PATCH RFC 01/10] rcu: Make CONFIG_SRCU unconditionally enabled

[Josh Triplett]

On Wed, Aug 08, 2018 at 01:17:44PM +0300, Kirill Tkhai wrote:
> On 08.08.2018 10:20, Michal Hocko wrote:
> > On Tue 07-08-18 18:37:36, Kirill Tkhai wrote:
> >> This patch kills all CONFIG_SRCU defines and
> >> the code under !CONFIG_SRCU.
> > 
> > The last time somebody tried to do this there was a pushback due to
> > kernel tinyfication. So this should really give some numbers about the
> > code size increase. Also why can't we make this depend on MMU. Is
> > anybody else than the reclaim asking for unconditional SRCU usage?
> 
> I don't know one. The size numbers (sparc64) are:
> 
> $ size image.srcu.disabled 
>    text	   data	    bss	    dec	    hex	filename
> 5117546	8030506	1968104	15116156	 e6a77c	image.srcu.disabled
> $ size image.srcu.enabled
>    text	   data	    bss	    dec	    hex	filename
> 5126175	8064346	1968104	15158625	 e74d61	image.srcu.enabled
> The difference is: 15158625-15116156 = 42469 ~41Kb

41k is a *substantial* size increase. However, can you compare
tinyconfig with and without this patch? That may have a smaller change.