From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>,
linux-arch <linux-arch@vger.kernel.org>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
X86 ML <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Nicolas Pitre <nicolas.pitre@linaro.org>,
Arnd Bergmann <arnd@arndb.de>,
Paul Burton <paul.burton@imgtec.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH] x86: enable dead code and data elimination (LTO)
Date: Sun, 9 Jul 2017 22:29:37 +0900 [thread overview]
Message-ID: <CAK7LNAR-VF2o3-qcCXnkath_B74KQodh_vezPRErGPhZSao2VA@mail.gmail.com> (raw)
In-Reply-To: <20170709090551.bm2c55ctt3togim7@gmail.com>
Hi.
2017-07-09 18:05 GMT+09:00 Ingo Molnar <mingo@kernel.org>:
>
> * Nicholas Piggin <npiggin@gmail.com> wrote:
>
>> FYI, easiest way to check if you forgot to KEEP a linker table is
>> to look at `readelf -S vmlinux` differences, and to see what is
>> being trimmed, look at nm differences or use --print-gc-sections
>> LD option to see what symbols you're trimming. Linker tables,
>> boot entry, and exception entry tends to require anchoring.
>
> Could you please add a debug build target to display all discarded
> symbols/sections? Something like:
>
> make lto-check
>
> ... or so?
>
> Thanks,
>
> Ingo
Actually, LTO activity existed some years ago
(but not pulled in).
http://www.spinics.net/lists/linux-kbuild/msg09242.html
IIUC, this patch enables "dead code elimination",
(or "garbage collection"?),
but I think it is different from what is called LTO.
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2017-07-09 13:29 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-09 3:13 [RFC PATCH] x86: enable dead code and data elimination (LTO) Nicholas Piggin
2017-07-09 9:05 ` Ingo Molnar
2017-07-09 13:29 ` Masahiro Yamada [this message]
2017-07-09 13:59 ` Nicolas Pitre
2017-07-10 2:13 ` Nicholas Piggin
2017-07-12 16:29 ` Andi Kleen
2017-07-12 17:34 ` Nicolas Pitre
2017-07-13 2:51 ` Nicholas Piggin
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