linux-kernel - Re: [GIT PULL] x86/alternatives padding

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Message-ID: <20150304112206.GB3516@pd.tnic>
Date:	Wed, 4 Mar 2015 12:22:06 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	x86-ml <x86@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	lkml <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/alternatives padding

On Wed, Mar 04, 2015 at 08:32:21AM +0100, Ingo Molnar wrote:
> Just curious: did the kernel image size change before/after these 
> changes? I.e. was any of the existing alternative instructions using 
> sites coded sub-optimally, with a larger maximum instruction size 
> allocated than strictly needed?
> 
> At least some of your improvements made things more optimal - 
> wondering at the total win, beyond the significant maintainability win 
> that is.

Well, kernel image doesn't change while vmlinux shows only a very small
.text increase of about 2K. I'm not sure yet why that happens though
because it shouldn't be the padding. Because we will have to do it
anyway, this patchset makes it automatic instead of by-hand, so to
speak.

Let me bisect it and see which patch adds the increase.

4.0-rc1 with alternatives patchset:
===================================

Setup is 15644 bytes (padded to 15872 bytes).
System is 5855 kB
CRC f2669897
Kernel: arch/x86/boot/bzImage is ready  (#1)

   text    data     bss     dec     hex filename
12292971        1595264 1085440 14973675         e47aeb vmlinux

plain 4.0-rc1:
==============

Setup is 15644 bytes (padded to 15872 bytes).
System is 5855 kB
CRC 7200607a
Kernel: arch/x86/boot/bzImage is ready  (#1)

   text    data     bss     dec     hex filename
12290539        1595264 1085440 14971243         e4716b vmlinux

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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