linux-kernel - Re: powerpc allyesconfig / allmodconfig linux-next next-20160729

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Message-ID: <20160804101051.39ca1e26@canb.auug.org.au>
Date:	Thu, 4 Aug 2016 10:10:51 +1000
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Nicholas Piggin <npiggin@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Luis R. Rodriguez" <mcgrof@...nel.org>,
	linux-next@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	linuxppc-dev@...ts.ozlabs.org, Guenter Roeck <linux@...ck-us.net>
Subject: Re: powerpc allyesconfig / allmodconfig linux-next next-20160729 -
 next-20160729 build failures

Hi Arnd,

On Wed, 03 Aug 2016 20:52:48 +0200 Arnd Bergmann <arnd@...db.de> wrote:
>
> Most of the difference appears to be in branch trampolines (634 added,
> 559 removed, 14837 unchanged) as you suspect, but I also see a couple
> of symbols show up in vmlinux that were not there before:
> 
> -A __crc_dma_noop_ops
> -D dma_noop_ops
> -R __clz_tab
> -r fdt_errtable
> -r __kcrctab_dma_noop_ops
> -r __kstrtab_dma_noop_ops
> -R __ksymtab_dma_noop_ops
> -t dma_noop_alloc
> -t dma_noop_free
> -t dma_noop_map_page
> -t dma_noop_mapping_error
> -t dma_noop_map_sg
> -t dma_noop_supported
> -T fdt_add_reservemap_entry
> -T fdt_begin_node
> -T fdt_create
> -T fdt_create_empty_tree
> -T fdt_end_node
> -T fdt_finish
> -T fdt_finish_reservemap
> -T fdt_property
> -T fdt_resize
> -T fdt_strerror
> -T find_cpio_data
> 
> 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.

You could try removing the --{,no-}whole-archive arguments to ld in
scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh.  Last time I did
that, though, a whole lot of stuff failed to be linked in. (Especially
stuff only referenced by EXPORT_SYMBOL()s, bu that may have been fixed).

> 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@...Ghz, just relinking vmlinux:

I was afraid of that, but it is offset by the time saved by not doing
the "ld -r"s along the way?  It may also be that (for powerpc anyway)
the linker is doing a better job.

-- 
Cheers,
Stephen Rothwell