linux-kernel - Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention

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Date:	Tue, 10 May 2016 21:02:18 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	x86-ml <x86@...nel.org>, Denys Vlasenko <dvlasenk@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Brian Gerst <brgerst@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andi Kleen <andi@...stfloor.org>, zengzhaoxiu@....com,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Zhaoxiu Zeng <zhaoxiu.zeng@...il.com>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH -v2] x86/hweight: Get rid of the special calling
 convention

On Tue, May 10, 2016 at 07:23:13PM +0200, Peter Zijlstra wrote:
> So what was wrong with using the normal thunk_*.S wrappers for the
> calls? That would allow you to use the alternative() stuff which does
> generate smaller code.

Yeah, so a full allyesconfig vmlinux gives ~22K .text size increase:

   text    data     bss     dec     hex filename
85391772        105899159       70717440        262008371       f9dee33 vmlinux 	before
85413991        105899223       70746112        262059326       f9eb53e vmlinux		after
--------
   22219

I guess I better try the thunk stuff, might make it smaller.

Also, in the next version I'll split out the static_cpu_has() move into
a separate patch, as you requested on IRC.

Thanks.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--