Re: [RFC PATCH v2] tinification: Introduce CONFIG_SRCU to make SRCU optional

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Thu, Dec 04, 2014 at 10:37:39AM -0500, Pranith Kumar wrote:
> On 12/04/2014 01:27 AM, Paul E. McKenney wrote:
> > For the moment, I applied this to -rcu against v3.18-rc6 to get some 0day
> > testing on it.
> > 
> > There are conflicts against the tip of my tree, but will worry about
> > that later.  I don't have a ready answer on whether or not this needs
> > to be split up -- in the worst case, we would add the SRCU Kconfig
> > parameter, add all the selects, then once they all hit mainline add the
> > Makefile change.
> > 
> > We will need stats on how much memory was saved, and a "size kernel/rcu/srcu.o"
> > after a UP/tiny build should do it.  Could you please add this to the
> > commit log?
> > 
> 
> So if we do not select CONFIG_SRCU, srcu.o will not be compiled at all. So we should save about
> 
>    text	   data	    bss	    dec	    hex	filename
>    2007	      0	      0	   2007	    7d7	kernel/rcu/srcu.o
> 
> as in size of arch/powerpc/boot/zImage changes from
> 
>    text	   data	    bss	    dec	    hex	filename
>  831552	  64180	  23944	 919676	  e087c	arch/powerpc/boot/zImage : before
>  829504	  64180	  23952	 917636	  e0084	arch/powerpc/boot/zImage : after
> 
> so about ~2000 bytes I guess. 

Nice!

Josh, I recall you having a tinified .config somewhere, but don't see it
right off.  If you do have one, could you please share it with Pranith?
Not a big deal, just don't want to overstate the savings too much.  ;-)

							Thanx, Paul