[PATCH v2] srcu: Isolate srcu sections using CONFIG_SRCU

Josh Triplett josh at joshtriplett.org
Mon Jan 5 15:57:54 AEDT 2015


<linux-s390 at vger.kernel.org>
Message-ID: <EA3B4EC8-5E29-4DA3-B826-52ABA92D7710 at joshtriplett.org>

On January 4, 2015 8:14:16 AM PST, "Paul E. McKenney" <paulmck at linux.vnet.ibm.com> wrote:
>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
><peterz at infradead.org> 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.

Agreed on both fronts; I don't think we should add any significant complexity just to turn link errors into compile errors.

- Josh Triplett



More information about the Linuxppc-dev mailing list