On Wed, 21 Jun 2017 09:19:13 -0700 Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote: > On 06/21, Arnd Bergmann wrote: > > On Wed, Jun 21, 2017 at 2:02 PM, Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > > > On Wed, 21 Jun 2017 13:32:17 +0200 > > > Arnd Bergmann <arnd@xxxxxxxx> wrote: > > > > > >> On Wed, Jun 21, 2017 at 1:10 PM, Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > > >> > On Wed, 21 Jun 2017 12:49:10 +0200 > > >> > Arnd Bergmann <arnd@xxxxxxxx> wrote: > > >> > > > >> >> 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: > > >> >> > > > >> >> > > >> >> 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/ > > >> > > > >> > Well I just mean the stuff now in kbuild/thin-ac, not the LD_DCDE. > > >> > Just want to try getting thin archives up to a point where there are > > >> > no serious regressions first. > > >> > > >> For my build testing, I have now reverted most of my patch and only > > >> left the 'select THIN_ARCHIVES'. I'll let you know if I run into problems. > > > > > > Okay. Currently with the patches in the kbuild tree, thin archives > > > actually does better than incremental linking for ARM (defconfig). > > > > > > 11651574 6090952 418616 18161142 1151df6 vmlinux.thinarc > > > 11656118 6095208 418952 18170278 11541a6 vmlinux.inc > > > > > > In mainline, thin archives is sub-optimal for lib-y libraries (just > > > pulls them all in). But now that I test it, even that is better than > > > incremental linking for ARM: > > > > > > 11653926 6090888 418620 18163434 11526ea vmlinux.thinarc > > > > > > I haven't grabbed that "clk: sunxi-ng: Move all clock types to a library" > > > patch yet to check. What tree is it in? I wonder if I could convince you > > > to drop that for now and bring it up on linux-kernel/linux-kbuild? I > > > think it's quite reasonable to reduce Kconfig hell of very fine grained > > > conditional compilation/linking if we can make the toolchain do it for > > > us. So we should consider how to support it nicely rather than having > > > such hacks IMO. > > > > [adding Maxime and Stephen to cc] > > > > Stephen, > > > > The hack has come to bite us after all, with Nick's proposed change to > > CONFIG_THIN_ARCHIVES for all architectures, the entire lib.a file will > > end up being linked into each kernel that enables the directory. > > > > I'm out of other ideas for fixing it, so it seems better to revert back to > > individual Kconfig options. Once we enable > > CONFIG_LD_DEAD_CODE_DATA_ELIMINATION (which is the > > next step after CONFIG_THIN_ARCHIVES), we can simply list > > all files, and the linker will drop all unused functions by itself. > > > > Ok. Can you send a revert patch to the list with some information > on why we can't do the hack anymore and also Cc lkml/kbuild > lists? The commit is in linux-next now as commit 06e226c7fb23 > (clk: sunxi-ng: Move all clock types to a library, 2017-06-02). > I grabbed this patch and applied it to the kbuid/thin-ac tree. I tested with thin archives enabled and disabled with arm defconfig which ends up setting CONFIG_SUNXI_CCU=y. The patch makes no difference to vmlinux size whether using traditional incremental link, or thin archives (there is a small difference between inclink and thinarc but that's unrelated). So this thin archives change does not break your patch, it's just that it doesn't really do the right thing. I like the general idea, but we need to work out how to make it properly supported by the build system. With the patch applied, this is what the build system currently does: arm-linux-gnueabihf-ld -EL -r -o drivers/clk/sunxi-ng/built-in.o drivers/clk/sunxi-ng/ccu-sun5i.o drivers/clk/sunxi-ng/ccu-sun6i-a31.o drivers/clk/sunxi-ng/ccu-sun8i-a23.o drivers/clk/sunxi-ng/ccu-sun8i-a33.o drivers/clk/sunxi-ng/ccu-sun8i-h3.o drivers/clk/sunxi-ng/ccu-sun8i-v3s.o drivers/clk/sunxi-ng/ccu-sun8i-r.o drivers/clk/sunxi-ng/ccu-sun9i-a80.o drivers/clk/sunxi-ng/ccu-sun9i-a80-de.o drivers/clk/sunxi-ng/ccu-sun9i-a80-usb.o drivers/clk/sunxi-ng/lib.a drivers/clk/sunxi-ng/lib-ksyms.o This incremental link pulls in all your lib.a objects and links them into built-in.o. They can no longer be selectively linked. Thanks, Nick
