Re: [PATCH 1/5] kbuild: thin archives final link close --whole-archives option

[Maxime Ripard <maxime.ripard@free-electrons.com>]

[-- Attachment #1: Type: text/plain, Size: 4359 bytes --]

On Fri, Jun 23, 2017 at 02:31:40PM +0900, Masahiro Yamada wrote:
> Hi Nicholas,
> 
> 2017-06-23 0:50 GMT+09:00 Nicholas Piggin <npiggin@gmail.com>:
> > On Thu, 22 Jun 2017 08:18:38 +0200
> > Maxime Ripard <maxime.ripard@free-electrons.com> wrote:
> >
> >> On Wed, Jun 21, 2017 at 10:55:06PM +0200, Arnd Bergmann wrote:
> >> > On Wed, Jun 21, 2017 at 8:08 PM, Nicholas Piggin <npiggin@gmail.com> wrote:
> >> > > On Wed, 21 Jun 2017 09:19:13 -0700
> >> > > Stephen Boyd <sboyd@codeaurora.org> wrote:
> >> > >> On 06/21, Arnd Bergmann wrote:
> >> > >>
> >> > >> 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.
> >> >
> >> > I think the ARM defconfig actually needs all those objects because it
> >> > enables all the high-level drivers. You could try disabling e.g. all except
> >> > CONFIG_SUN8I_DE2_CCU if you want the objects to actually becomes
> >> > unused.
> >>
> >> You can also disable MACH_SUN8I, it should disable a significant
> >> number of the clocks driver.
> >
> >    text    data     bss     dec     hex filename
> > 11655078        6018736  418944 18092758        11412d6 vmlinux.inclink
> > 11655078        6018736  418944 18092758        11412d6 vmlinux.inclink.clk
> > 11650534        6010288  418616 18079438        113dece vmlinux.thinarc
> > 11650534        6010288  418616 18079438        113dece vmlinux.thinarc.clk
> >
> > Same result for me when compiling defconfig minus MACH_SUN8I, comparing
> > +/- the clock patch and thin archives. No size savings. As I explained
> > already, I really can't see how there could be any saving if the lib.a is
> > incrementally linked into built-in.o.
> 
> I think defconfig minus MACH_SUN8I
> will give no difference to CONFIG_SUNXI_CCU*
> 
> As far as I tried,  minus MACH_SUN8I still enabled the following:
> CONFIG_SUNXI_CCU=y
> CONFIG_SUNXI_CCU_DIV=y
> CONFIG_SUNXI_CCU_FRAC=y
> CONFIG_SUNXI_CCU_GATE=y
> CONFIG_SUNXI_CCU_MUX=y
> CONFIG_SUNXI_CCU_MULT=y
> CONFIG_SUNXI_CCU_PHASE=y
> CONFIG_SUNXI_CCU_NK=y
> CONFIG_SUNXI_CCU_NKM=y
> CONFIG_SUNXI_CCU_NKMP=y
> CONFIG_SUNXI_CCU_NM=y
> CONFIG_SUNXI_CCU_MP=y
> 
> I think you need to disable some more MACH_SUN*I and
> perhaps disable some CONFIG_SUN*I_*_CCU explicitly,
> then you will see difference in the result.

Ah, right, it's all selected by the rest.

I guess to get a meaningful example you could disable all the
SUN*I_CCU (SUN5I, SUN8I, and the likes) options and while keeping
SUN8I_R_CCU.

Most of the clock types shouldn't be used but div and gates.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 801 bytes --]