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From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: [PATCH 1/2] kbuild: remove top-level built-in.a
Date: Tue, 15 Jan 2019 18:01:34 +0900	[thread overview]
Message-ID: <CAK7LNAREyw=qhRO-Cvg4O2fOnbV=zVJDE_mRZcVTkKG+B1gkRQ@mail.gmail.com> (raw)
In-Reply-To: <1547536378.afs6amsrzj.astroid@bobo.none>

Hi Nicholas,


On Tue, Jan 15, 2019 at 5:07 PM Nicholas Piggin <npiggin@gmail.com> wrote:
>
> Masahiro Yamada's on January 14, 2019 1:27 pm:
> > The symbol table in the final archive is unneeded because it is passed
> > to the linker after the --whole-archive option. Every object file in
> > the archive is included in the link anyway.
> >
> > Pass thin archives from subdirectories directly to the linker, and
> > remove the final archiving step.
>
> This seems like a good improvement. As far as I remember, it was slower
> to do the final link without the index built. Maybe I was testing it
> in a revision before moving those files into --whole-archive? If there
> is no slowdown, then I have no objection.


Thanks for the review.


I measured the performance of scripts/link-vmlinux.sh with 'perf stat'.
(20 times for each)



Before this patch:

 Performance counter stats for 'make vmlinux' (20 runs):

       5.266796537 seconds time elapsed
          ( +-  0.12% )



After this patch:

 Performance counter stats for 'make vmlinux' (20 runs):

       4.945576395 seconds time elapsed




So, the performance is slightly better.

Maybe, does omitting the 'ar' save some time?


Anyway, this commit is good.


-- 
Best Regards
Masahiro Yamada

  reply	other threads:[~2019-01-15  9:02 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-14  3:27 [PATCH 1/2] kbuild: remove top-level built-in.a Masahiro Yamada
2019-01-14  3:27 ` [PATCH 2/2] kbuild: merge KBUILD_VMLINUX_{INIT,MAIN} into KBUILD_VMLINUX_OBJS Masahiro Yamada
2019-01-15  7:15 ` [PATCH 1/2] kbuild: remove top-level built-in.a Nicholas Piggin
2019-01-15  9:01   ` Masahiro Yamada [this message]
2019-01-23  8:26     ` Nicholas Piggin

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