Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures

From	Arnd Bergmann <arnd@arndb.de>
Newsgroups	linux.kernel
Subject	Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures
Date	2016-08-11 15:10 +0200
Message-ID	<s4XUd-4eY-5@gated-at.bofh.it> (permalink)
References	<s1OaK-WW-15@gated-at.bofh.it> <s2aNY-7my-17@gated-at.bofh.it> <s4XAR-3T5-3@gated-at.bofh.it>
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On Thursday, August 11, 2016 10:43:20 PM CEST Nicholas Piggin wrote:
> On Wed, 03 Aug 2016 22:13:28 +0200
> Arnd Bergmann <arnd@arndb.de> wrote:
> 
> > On Wednesday, August 3, 2016 2:44:29 PM CEST Segher Boessenkool wrote:
> > > Hi Arnd,
> > > 
> > > On Wed, Aug 03, 2016 at 08:52:48PM +0200, Arnd Bergmann wrote:  
> > > > From my first look, it seems that all of lib/*.o is now getting linked
> > > > into vmlinux, while we traditionally leave out everything from lib/
> > > > that is not referenced.
> > > > 
> > > > I also see a noticeable overhead in link time, the numbers are for
> > > > a cache-hot rebuild after a successful allyesconfig build, using a
> > > > 24-way Opteron@2.5Ghz, just relinking vmlinux:
> > > > 
> > > > $ time make skj30 vmlinux # before
> > > > real	2m8.092s
> > > > user	3m41.008s
> > > > sys	0m48.172s
> > > > 
> > > > $ time make skj30 vmlinux # after
> > > > real	4m10.189s
> > > > user	5m43.804s
> > > > sys	0m52.988s  
> > > 
> > > Is it better when using rcT instead of rcsT?  
> > 
> > It seems to be noticeably better for the clean rebuild case, though
> > not as good as the original:
> > 
> > real	3m34.015s
> > user	5m7.104s
> > sys	0m49.172s
> > 
> > I've also tried now with my own patch applied as well (linking
> > each drivers/*/built-in.o into vmlinux rather than having them
> > linked into drivers/built-in.o first), but that makes no
> > difference.
> 
> I just want to come back to this, because I've subbmitted the thin
> archives kbuild patch, I wanted to make sure we're doing okay on
> ARM/ARM64. I cross compiled with my laptop.
> 
> For ARM64 allyesconfig:
> 
> After building then removing all built-in.o then rebuilding vmlinux:
> inclink
> time make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j8 vmlinux
> real    1m18.977s
> user    2m14.512s
> sys     0m29.704s
> 
> thinarc
> time make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j8 vmlinux
> real    1m18.433s
> user    2m6.128s
> sys     0m28.372s
> 
> 
> Final ld time
> inclink
> real    0m4.005s
> user    0m3.464s
> sys     0m0.536s
> 
> thinarc
> real    0m5.841s
> user    0m4.916s
> sys     0m0.916s
> 
> 
> Build directory size is of course much better (3953MB vs 5519MB).

Ok, looks great. Some downsides and some upsides here, but overall
I think this is a win.

> 
> For ARM, defconfig
> 
> After building then removing all built-in.o then rebuilding vmlinux:
> inclink
> real	0m19.593s
> user	0m22.372s
> sys	0m6.428s
> 
> thinarc
> real	0m18.919s
> user	0m21.924s
> sys	0m6.400s
> 
> 
> Final ld time
> inclink
> real	0m0.378s
> user	0m0.304s
> sys	0m0.076s
> 
> thinarc
> real    0m0.894s
> user    0m0.684s
> sys     0m0.200s

This also still seems fine.

> For both cases final link gets slower with thin archives. I guess there is some
> per-file overhead but I thought with --whole-archive it should not be that much
> slower. Still, overall time for main ar/ld phases comes out about the same in
> the end so I don't think it's too much problem. Unless ARM blows up significantly
> worse with a bigger config.

Unfortunately I think it does. I haven't tried your latest series yet,
but I think the total time for removing built-in.o and relinking went
up from around 4 minutes (already way too much) to 18 minutes for me.

> Linking with thin archives takes significantly more time in bfd hash lookup code.
> I haven't dug much further yet.

Can you try the ARM allyesconfig with thin archives? I'll follow up with two
patches: one to get ARM to link without thin archives, and one that I used
to get --gc-sections to work.

	Arnd

Thread

powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-08-02 22:10 +0200
  Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Guenter Roeck <linux@roeck-us.net> - 2016-08-03 00:00 +0200
    Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-08-03 00:30 +0200
      Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-03 00:50 +0200
      Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Stephen Rothwell <sfr@canb.auug.org.au> - 2016-08-03 02:30 +0200
        Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-03 10:00 +0200
          Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Stephen Rothwell <sfr@canb.auug.org.au> - 2016-08-03 14:30 +0200
            Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-03 14:40 +0200
              Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-03 18:00 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-03 21:10 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-03 22:20 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-11 14:50 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-11 15:10 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-11 15:20 +0200
                [TESTING] kbuild: link drivers subdirectories separately Arnd Bergmann <arnd@arndb.de> - 2016-08-11 16:00 +0200
                Re: [TESTING] kbuild: link drivers subdirectories separately Arnd Bergmann <arnd@arndb.de> - 2016-08-11 17:50 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Segher Boessenkool <segher@kernel.crashing.org> - 2016-08-03 22:50 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Stephen Rothwell <sfr@canb.auug.org.au> - 2016-08-04 02:20 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-04 11:10 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-04 12:50 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-04 13:50 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-04 14:20 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-04 14:40 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-04 17:50 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-04 18:10 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-04 18:20 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Segher Boessenkool <segher@kernel.crashing.org> - 2016-08-04 20:30 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-05 10:50 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-05 12:20 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-05 14:30 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-05 18:10 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-05 18:20 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-05 21:20 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -  next-20160729 build failures Nicholas Piggin <npiggin@gmail.com> - 2016-08-06 22:50 +0200
                Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Arnd Bergmann <arnd@arndb.de> - 2016-08-06 23:20 +0200
  Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 - next-20160729 build failures Michael Ellerman <mpe@ellerman.id.au> - 2016-08-03 05:30 +0200

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