From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755857AbbIYLo1 (ORCPT <rfc822;w@1wt.eu>);
	Fri, 25 Sep 2015 07:44:27 -0400
Received: from mail.skyhub.de ([78.46.96.112]:40898 "EHLO mail.skyhub.de"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1754255AbbIYLoZ (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 25 Sep 2015 07:44:25 -0400
Date: Fri, 25 Sep 2015 13:44:23 +0200
From: Borislav Petkov <bp@alien8.de>
To: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@amacapital.net>,
        "H. Peter Anvin" <hpa@zytor.com>, Brian Gerst <brgerst@gmail.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/processor.h: Force inlining of cpu_relax()
Message-ID: <20150925114423.GD3568@pd.tnic>
References: <1443096149-27291-1-git-send-email-dvlasenk@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <1443096149-27291-1-git-send-email-dvlasenk@redhat.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Sep 24, 2015 at 02:02:29PM +0200, Denys Vlasenko wrote:
> On x86, cpu_relax() simply calls rep_nop(), which generates one
> instruction, PAUSE (aka REP NOP).
> 
> With this config:
> http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os
> gcc-4.7.2 does not always inline rep_nop(): it generates
> several copies of this:
> 
> <rep_nop> (16 copies, 194 calls):
>        55                      push   %rbp
>        48 89 e5                mov    %rsp,%rbp
>        f3 90                   pause
>        5d                      pop    %rbp
>        c3                      retq
> 
> See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122
> 
> This patch fixes this via s/inline/__always_inline/
> on rep_nop() and cpu_relax().
> (Forcing inlining only on rep_nop() causes gcc to
> deinline cpu_relax(), with almost no change in generated code).
> 
>     text     data      bss       dec     hex filename
> 88118971 19905208 36421632 144445811 89c1173 vmlinux.before
> 88118139 19905208 36421632 144444979 89c0e33 vmlinux

Looks ok to me, text even grows smaller.

Acked-by: Borislav Petkov <bp@suse.de>

-- 
Regards/Gruss,
    Boris.

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