On Mon, 29 May 2017 20:52:51 +0200 Sam Ravnborg <sam@xxxxxxxxxxxx> wrote: > Hi Nicholas. > > > Supporting two different intermediate-artifact packaging schemes > > was only ever intended as a temporary transition. > > > > This has so far caused no problems for powerpc, after a small fix > > for how the arch invoked ar. So now allow any arch to select the > > option, continue defaulting to N. > > Alan Modra recommended this approach several years ago, and I think > Stephen was the first to implement this for the kernel. > It would be good to have the rational whay ar is better than ld -r > included in the commit message for later reference. We *are* using Stephen's thin archives build infrastructure in the kernel already. Only powerpc is using it so far: a5967db9af The big one for powerpc build is that the linker keeps relative location of input sections the same, so as you link into larger built-in.o files, there is less opportunity to place code optimally. x86 may not care so much, but some other archs will. The build output size improvement is nice for everyone though. > I also recall that using ar gave some small kernel size reductions > from last time we played with this. > This info could also be nice to give a rough idea of the impact. There is some explanation in sfr's patch. It's not thin archives as such, but rather we have to link with --whole-archive, but it was a very small impact. IIRC today's final link is technically buggy without that option, it's just that in practice the top-level built-in.o files pull in so much that the linker will never discard one. Thanks, Nick -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
