linux-kernel - Re: [PATCH] x86, mtrr: mark range_new in mtrr_calc_range_state() as _

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Date:	Fri, 27 Nov 2015 10:31:25 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
	Toshi Kani <toshi.kani@...com>
Subject: Re: [PATCH] x86, mtrr: mark range_new in mtrr_calc_range_state() as
 __initdata


* Rasmus Villemoes <linux@...musvillemoes.dk> wrote:

> range_new doesn't seem to be used after init. It is only passed to
> memset, sum_ranges, memcmp and x86_get_mtrr_mem_range, the latter of
> which also only passes it on to various *range* library functions. So
> mark it __initdata to free up an extra page after init.
> 
> nr_range_new is unconditionally assigned to before it is read, so
> there's no point in having it static.
> 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
>  arch/x86/kernel/cpu/mtrr/cleanup.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c
> index 70d7c93f4550..b1a9ad366f67 100644
> --- a/arch/x86/kernel/cpu/mtrr/cleanup.c
> +++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
> @@ -593,9 +593,9 @@ mtrr_calc_range_state(u64 chunk_size, u64 gran_size,
>  		      unsigned long x_remove_base,
>  		      unsigned long x_remove_size, int i)
>  {
> -	static struct range range_new[RANGE_NUM];
> +	static struct range range_new[RANGE_NUM] __initdata;
>  	unsigned long range_sums_new;
> -	static int nr_range_new;
> +	int nr_range_new;
>  	int num_reg;
>  
>  	/* Convert ranges to var ranges state: */

So this static variable actually surprised me - I never realized it was there - 
and it's not some simple 'once' flag, but something that is essential semantics.

So marking it __initdata is correct, but please also move it out of function local 
variables scope, into file scope - and name it properly as well, like 
mtrr_new_range[] or so?

Thanks,

	Ingo
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