On Wed, Jun 21, 2017 at 11:16 AM, Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > On Wed, 21 Jun 2017 09:15:09 +0200 > Arnd Bergmann <arnd@xxxxxxxx> wrote: > >> On Wed, Jun 21, 2017 at 6:04 AM, Nicholas Piggin <npiggin@xxxxxxxxx> wrote: >> > On Wed, 21 Jun 2017 12:29:33 +0900 >> > Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> wrote: >> >> >> BTW, I saw abuse of lib.a in >> >> https://patchwork.kernel.org/patch/9768439/ >> >> >> >> I see it in linux-next. >> >> >> >> commit 06e226c7fb233f676b01b144d0b321ebe510fdcd >> >> Author: Stephen Boyd <sboyd@xxxxxxxxxxxxxx> >> >> Date: Fri Jun 2 15:30:06 2017 -0700 >> >> >> >> clk: sunxi-ng: Move all clock types to a library >> >> >> >> >> >> >> >> >> >> Now drivers/clk/sunxi-ng/lib.a >> >> will go into thin archives. >> >> The result might be different from what they expect... >> > >> > Yes I see. With thin archives, that is just going to cause the >> > same behaviour as built-in.o (everything will be linked). So the >> > build should not break, but they won't get savings. >> > >> > Does it even save space with incremental linking? If the lib.a gets >> > linked into drivers/built-in.o, I wonder what happens then? >> >> Ah, too bad. I thought we had found a way to use a library correctly >> here, but I just verified that indeed all the just gets linked into built-in.o >> >> I played around with it some more now, but without success: if I >> build sunxi-ng as a loadable module (using a few modifications), >> then the unneeded objects from lib.a are dropped as I had hoped, >> but for built-in code we now always include everything. >> >> I suppose that we can ignore this once we get >> LD_DEAD_CODE_DATA_ELIMINATION enabled on ARM, but >> until then, we have a code size regression. > > I didn't follow the thread there, is it a regression caused by > thin archives, or just by removing the Kconfig symbol from each > file? I thought it was the latter, but actually it only happens with thin archives, so we are fine as long as we enable THIN_ARCHIVES and LD_DEAD_CODE_DATA_ELIMINATION at the same time on ARM. Arnd
