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[193.116.78.72]) by smtp.gmail.com with ESMTPSA id s79sm32756271pgs.50.2019.01.23.00.26.45 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 23 Jan 2019 00:26:48 -0800 (PST) Date: Wed, 23 Jan 2019 18:26:35 +1000 From: Nicholas Piggin Subject: Re: [PATCH 1/2] kbuild: remove top-level built-in.a To: Masahiro Yamada Cc: Linux Kbuild mailing list , Linux Kernel Mailing List , Stephen Rothwell References: <1547436479-10491-1-git-send-email-yamada.masahiro@socionext.com> <1547536378.afs6amsrzj.astroid@bobo.none> In-Reply-To: MIME-Version: 1.0 User-Agent: astroid/0.14.0 (https://github.com/astroidmail/astroid) Message-Id: <1548231946.lwdxf373y2.astroid@bobo.none> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Masahiro Yamada's on January 15, 2019 7:01 pm: > Hi Nicholas, >=20 >=20 > On Tue, Jan 15, 2019 at 5:07 PM Nicholas Piggin 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. >=20 >=20 > Thanks for the review. >=20 >=20 > I measured the performance of scripts/link-vmlinux.sh with 'perf stat'. > (20 times for each) >=20 >=20 >=20 > Before this patch: >=20 > Performance counter stats for 'make vmlinux' (20 runs): >=20 > 5.266796537 seconds time elapsed > ( +- 0.12% ) >=20 >=20 >=20 > After this patch: >=20 > Performance counter stats for 'make vmlinux' (20 runs): >=20 > 4.945576395 seconds time elapsed >=20 >=20 >=20 >=20 > So, the performance is slightly better. >=20 > Maybe, does omitting the 'ar' save some time? Wow yeah that's a good speedup and simplification to boot. Thanks for=20 checking it. > Anyway, this commit is good. Yes, it's a good improvement. Thanks, Nick =