linux-kernel - Re: [PATCH 16/28] ktap: add runtime/amalg.c

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Date:	Sat, 29 Mar 2014 15:38:38 +0800
From:	Jovi Zhangwei <jovi.zhangwei@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 16/28] ktap: add runtime/amalg.c

Hi,

On Sat, Mar 29, 2014 at 2:52 AM, Andi Kleen <andi@...stfloor.org> wrote:
> Jovi Zhangwei <jovi.zhangwei@...il.com> writes:
>
>> Use amalgamation build make ktapvm.ko much smaller.
>>
>> No amalgamation build in x86_64:
>> ktapvm.ko: 2.4M
>>
>> amalgamation build in x86_64:
>> ktapvm.ko: 1.1M
>>
>> User can set use amalgamation build or not in Makefile.
>
> This seems dubious. Is that due to debug information?
>
> [if yes new enough toolchain can fix that]
>
> If it's due to code something is seriously wrong,
> perhaps in your inlines.
>

Change: The kernel module size without amalgamation build is: 3.1M

I guess it's not because of debug info.

Amalgamation build is a kind of simple 'LTO', it compiles the ktapvm as
one huge C file and allows GCC to generate faster and shorter code.

But I also surprised by the size gap, will spend some time to investigate it.

Thanks.

Jovi
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