linux-kernel - Re: [PATCH -v1.1] x86: Optimize clear

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Date:   Sun, 19 Feb 2017 14:41:09 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v1.1] x86: Optimize clear_page()

On Wed, Feb 15, 2017 at 12:19:27PM +0100, Borislav Petkov wrote:
> Here's a fixed version of the breakage the 0day bot reported:
> 
> ---
> From: Borislav Petkov <bp@...e.de>
> Date: Thu, 9 Feb 2017 01:34:49 +0100
> Subject: [PATCH -v1.1] x86: Optimize clear_page()
> 
> Currently, we CALL clear_page() which then JMPs to the proper function
> chosen by the alternatives.
> 
> What we should do instead is CALL the proper function directly. (This
> was something Ingo suggested a while ago). So let's do that.
> 
> Measuring our favourite kernel build workload shows that there are no
> significant changes in performance.

...

> Signed-off-by: Borislav Petkov <bp@...e.de>
> [ Forgot to add clobbers. ]
> Reported-by: kernel test robot <fengguang.wu@...el.com>

Fengguang just confirmed too:

"Yes it works fine for 300 boots.

Tested-by: Fengguang Wu <fengguang.wu@...el.com>"

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.