linux-kernel - Re: [PATCH v5 01/11] thp: huge zero page: basic preparation

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Date:	Wed, 14 Nov 2012 14:09:49 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill@...temov.name>
Subject: Re: [PATCH v5 01/11] thp: huge zero page: basic preparation

On Wed, 7 Nov 2012, Kirill A. Shutemov wrote:

> From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> 
> Huge zero page (hzp) is a non-movable huge page (2M on x86-64) filled
> with zeros.
> 
> For now let's allocate the page on hugepage_init(). We'll switch to lazy
> allocation later.
> 
> We are not going to map the huge zero page until we can handle it
> properly on all code paths.
> 
> is_huge_zero_{pfn,pmd}() functions will be used by following patches to
> check whether the pfn/pmd is huge zero page.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

Acked-by: David Rientjes <rientjes@...gle.com>

> ---
>  mm/huge_memory.c |   30 ++++++++++++++++++++++++++++++
>  1 files changed, 30 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 40f17c3..e5ce979 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -47,6 +47,7 @@ static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
>  /* during fragmentation poll the hugepage allocator once every minute */
>  static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
>  static struct task_struct *khugepaged_thread __read_mostly;
> +static unsigned long huge_zero_pfn __read_mostly;
>  static DEFINE_MUTEX(khugepaged_mutex);
>  static DEFINE_SPINLOCK(khugepaged_mm_lock);
>  static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
> @@ -159,6 +160,29 @@ static int start_khugepaged(void)
>  	return err;
>  }
>  
> +static int init_huge_zero_page(void)

Could be __init, but this gets switched over to lazy allocation later in 
the series so probably not worth it.
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