Re: [PATCH] hugetlb, x86: register 1G page size if we can allocate them runtime

[Luiz Capitulino <lcapitulino@redhat.com>]

On Wed,  4 Feb 2015 13:54:31 +0200
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> wrote:

> After commit 944d9fec8d7a we can allocate 1G pages runtime if CMA is
> enabled.
> 
> Let's register 1G pages into hugetlb even if user hasn't requested them
> explicitly at boot time with hugepagesz=1G.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Luiz Capitulino <lcapitulino@redhat.com>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> ---
>  arch/x86/mm/hugetlbpage.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
> index 9161f764121e..42982b26e32b 100644
> --- a/arch/x86/mm/hugetlbpage.c
> +++ b/arch/x86/mm/hugetlbpage.c
> @@ -172,4 +172,15 @@ static __init int setup_hugepagesz(char *opt)
>  	return 1;
>  }
>  __setup("hugepagesz=", setup_hugepagesz);
> +
> +#ifdef CONFIG_CMA
> +static __init int gigantic_pages_init(void)
> +{
> +	/* With CMA we can allocate gigantic pages at runtime */
> +	if (cpu_has_gbpages && !size_to_hstate(1UL << PUD_SHIFT))
> +		hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
> +	return 0;
> +}
> +arch_initcall(gigantic_pages_init);
> +#endif
>  #endif

Very nice! I was thinking about this for a long time but I don't
think my implementation would be that simple:

Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>