From: Nicolas Pitre <nico@fluxnic.net>
To: Andi Kleen <andi@firstfloor.org>
Cc: npiggin@gmail.com, linux-kernel@vger.kernel.org,
linux-kbuild@vger.kernel.org
Subject: Re: [RFC PATCH] x86: enable dead code and data elimination (LTO)
Date: Wed, 12 Jul 2017 13:34:46 -0400 (EDT) [thread overview]
Message-ID: <alpine.LFD.2.20.1707121331060.1959@knanqh.ubzr> (raw)
In-Reply-To: <87a849aaa3.fsf@firstfloor.org>
On Wed, 12 Jul 2017, Andi Kleen wrote:
> Nicholas Piggin <npiggin@gmail.com> writes:
> >>
> >> I think we should aim for gc-sections to be used by default and have LTO
> >> as a possible option only.
> >
> > I agree after it starts getting implemented and debugged by small
> > system users, we could make it default in the interest of sharing
> > testing and reducing combinations.
>
> From what i understand the main drawback in the past was
> is that various linker versions become very slow with thousands of
> sections.
>
> So it may cost you built time. For a special small build it's probably
> ok, but you wouldn't want to make it default.
>
> Also usually it's only useful without modules because if you
> use modules EXPORT_SYMBOL pulls in a lot of unused functions.
I created CONFIG_TRIM_UNUSED_KSYMS mainly to avoid that issue. It is
highly effective with either gc-sections and LTO.
Nicolas
next prev parent reply other threads:[~2017-07-12 17:41 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
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 [this message]
2017-07-13 2:51 ` Nicholas Piggin
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