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Subject: Re: Prezeroing V3 [1/4]: Allow request for zeroed memory
From: Dave Hansen <haveblue@us.ibm.com>
To: Christoph Lameter <clameter@sgi.com>
Cc: Andrew Morton <akpm@osdl.org>, linux-ia64@vger.kernel.org,
       Linus Torvalds <torvalds@osdl.org>, linux-mm <linux-mm@kvack.org>,
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Date: Tue, 04 Jan 2005 15:45:42 -0800
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On Tue, 2005-01-04 at 15:13 -0800, Christoph Lameter wrote:
> +		if (gfp_flags & __GFP_ZERO) {
> +#ifdef CONFIG_HIGHMEM
> +			if (PageHighMem(page)) {
> +				int n = 1 << order;
> +
> +				while (n-- >0)
> +					clear_highpage(page + n);
> +			} else
> +#endif
> +			clear_page(page_address(page), order);
> +		}
>  		if (order && (gfp_flags & __GFP_COMP))
>  			prep_compound_page(page, order);

That #ifdef can probably die.  The compiler should get that all by
itself:

> #ifdef CONFIG_HIGHMEM
> #define PageHighMem(page)       test_bit(PG_highmem, &(page)->flags)
> #else
> #define PageHighMem(page)       0 /* needed to optimize away at compile time */
> #endif

-- Dave