From: "Mihai Donțu" <mihai.dontu@gmail.com>
To: Jeff Merkey <linux.mdb@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: x86_64 Compiler Output Kernel Bloat v4.4
Date: Tue, 19 Jan 2016 00:12:11 +0200 [thread overview]
Message-ID: <20160119001211.3fd67d31@mdontu-l.dsd.ro> (raw)
In-Reply-To: <CAO6TR8Wj3nGh0MMd3mhXXmUxQ78bGBRSMN3ShD36aofAso1jMQ@mail.gmail.com>
On Mon, 18 Jan 2016 14:45:48 -0700 Jeff Merkey wrote:
> On 1/18/16, Jeff Merkey <linux.mdb@gmail.com> wrote:
> > On 1/18/16, Jeff Merkey <linux.mdb@gmail.com> wrote:
> > > I noticed that in the assembler output for the x86_64 builds almost
> > > every single function originating from C code has a nop instruction
> > > that prefaces the function call. I guess the concern with this is
> > > the wasted space issue as each one of these placeholders takes up a
> > > bunch of bytes at the head of each function. Is there a reason this
> > > assembler header is there in the first place to anyones knowledge?
> > > Since every single function just about is prefaced by this inert 5
> > > byte instruction it adds up to quite a bit of bloat in the size of the
> > > linux executable.
If I'm not mistaking, those bytes are used to dynamically enable ftrace:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/trace/ftrace-design.txt
--
Mihai Donțu
next prev parent reply other threads:[~2016-01-18 22:12 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-18 21:29 Jeff Merkey
2016-01-18 21:34 ` Jeff Merkey
2016-01-18 21:45 ` Jeff Merkey
2016-01-18 21:45 ` Jeff Merkey
2016-01-18 22:12 ` Mihai Donțu [this message]
2016-01-19 7:39 ` Jiri Olsa
2016-01-19 15:32 ` Jeff Merkey
2016-01-19 15:47 ` Jeff Merkey
2016-01-20 14:40 ` Steven Rostedt
2016-01-20 14:46 ` H. Peter Anvin
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