linux-kernel - Re: [PATCH 4/5] -march=native: REP STOSB

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Date:   Fri, 08 Dec 2017 11:08:04 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com
Subject: Re: [PATCH 4/5] -march=native: REP STOSB

Alexey Dobriyan <adobriyan@...il.com> writes:
>  
> +#ifdef CONFIG_MARCH_NATIVE_REP_STOSB
> +static __always_inline void clear_page(void *page)
> +{
> +	uint32_t len = PAGE_SIZE;
> +	asm volatile (
> +		"rep stosb"
> +		: "+D" (page), "+c" (len)
> +		: "a" (0)
> +		: "memory"
> +	);
> +}

clear_page_64 already patches in the equivalent code sequence,
it's clear_page_erms()

It's very doubtful that this patch is worth it.

-Andi