On Wed, Jun 21, 2017 at 12:38 PM, Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > On Wed, 21 Jun 2017 12:21:16 +0200 > Arnd Bergmann <arnd@xxxxxxxx> wrote: > >> 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, > > Is this including these changes now in the kbuild tree? I'm building on top of yesterday's linux-next at the moment, with a number of my own patches applied > I can take a look at ARM and try to get it at least to parity with > incremental link. Any particular config options required? This is the patch I am testing with: https://pastebin.com/HQuhCEmK I have not looked at that in a while, no idea if it works, or if it has known problems. I last posted the patch in March for discussion: https://patchwork.kernel.org/patch/9626207/ >> so we are fine as long as we enable THIN_ARCHIVES >> and LD_DEAD_CODE_DATA_ELIMINATION at the same time >> on ARM. > > Well the current proposal is to unconditionally enable it for all archs > for 4.13. After that I'll submit patches to x86 and powerpc arch > maintainers to allow LD_DEAD_CODE_DATA_ELIMINATION as an option. I guess > you will do ARM and there have been MIPS guys looking at it too. > > That leaves a window of one release. ARM could unselect thin archives if > necessary but I think it would be much better to enable it and flush out > any toolchain and build issues before doing the LD_DCDE option. Disabling > should be a last resort if we can't fix something in time for release. I see. Arnd -- 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
