Subject: Re: [PATCH v2] srcu: Isolate srcu sections using CONFIG_SRCU

From: "Paul E. McKenney" <[email-masked]>
Date: Sun, 4 Jan 2015 08:14:16 -0800

On Sun, Jan 04, 2015 at 08:35:52PM +1100, Michael Ellerman wrote:
> On Tue, 2014-12-30 at 13:54 -0500, Pranith Kumar wrote:
> > On Tue, Dec 30, 2014 at 1:50 PM, Peter Zijlstra <[email-masked]> wrote:
> > > On Tue, Dec 30, 2014 at 12:46:22AM -0500, Pranith Kumar wrote:
> > >> Isolate the SRCU functions and data structures within CONFIG_SRCU so that there
> > >> is a compile time failure if srcu is used when not enabled. This was decided to
> > >> be better than waiting until link time for a failure to occur.
> > >
> > > Why?
> > 
> > This is part of the kernel tinification efforts. The first patch was
> > posted here: https://lkml.org/lkml/2014/12/4/848. This patch enables a
> > compile time failure instead of a link time failure.
> 
> The punch line was:
> 
>   "so the savings are about ~2000 bytes."
> 
> Which is utterly not worth the effort IMO. There have got to be more attractive
> targets for tinification than this.

There probably are.  But if the tinification effort is to come anywhere
near reaching its goals, it is going to need 2000-byte savings, especially
on the small systems that are this effort's main target.

That said, Peter's suggestion of falling back to the link-time diagnostic
does simplify things a bit, and might be a good approach.

							Thanx, Paul