linux-kernel - Re: [PATCH] mm/hugetlb: use helper huge_page

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Date:   Mon, 8 Feb 2021 16:45:46 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/hugetlb: use helper huge_page_size() to get hugepage
 size

On 2/8/21 12:24 AM, Miaohe Lin wrote:
> We can use helper huge_page_size() to get the hugepage size directly to
> simplify the code slightly.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  mm/hugetlb.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 18628f8dbfb0..6cdb59d8f663 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3199,7 +3199,7 @@ void __init hugetlb_add_hstate(unsigned int order)
>  	BUG_ON(order == 0);
>  	h = &hstates[hugetlb_max_hstate++];
>  	h->order = order;
> -	h->mask = ~((1ULL << (order + PAGE_SHIFT)) - 1);
> +	h->mask = ~(huge_page_size(h) - 1);
>  	for (i = 0; i < MAX_NUMNODES; ++i)
>  		INIT_LIST_HEAD(&h->hugepage_freelists[i]);
>  	INIT_LIST_HEAD(&h->hugepage_activelist);
> @@ -3474,7 +3474,7 @@ void hugetlb_report_meminfo(struct seq_file *m)
>  	for_each_hstate(h) {
>  		unsigned long count = h->nr_huge_pages;
>  
> -		total += (PAGE_SIZE << huge_page_order(h)) * count;
> +		total += huge_page_size(h) * count;
>  
>  		if (h == &default_hstate)
>  			seq_printf(m,
> @@ -3487,10 +3487,10 @@ void hugetlb_report_meminfo(struct seq_file *m)
>  				   h->free_huge_pages,
>  				   h->resv_huge_pages,
>  				   h->surplus_huge_pages,
> -				   (PAGE_SIZE << huge_page_order(h)) / 1024);
> +				   huge_page_size(h) / SZ_1K);
>  	}
>  
> -	seq_printf(m, "Hugetlb:        %8lu kB\n", total / 1024);
> +	seq_printf(m, "Hugetlb:        %8lu kB\n", total / SZ_1K);
>  }
>  
>  int hugetlb_report_node_meminfo(char *buf, int len, int nid)
> @@ -3524,7 +3524,7 @@ void hugetlb_show_meminfo(void)
>  				h->nr_huge_pages_node[nid],
>  				h->free_huge_pages_node[nid],
>  				h->surplus_huge_pages_node[nid],
> -				1UL << (huge_page_order(h) + PAGE_SHIFT - 10));
> +				huge_page_size(h) >> 10);

Should we change this to

				huge_page_size(h) / SZ_1K);

as in hugetlb_report_meminfo above?  Or, is that one where it takes an
additional instruction to do the divide as opposed to the shift?  I would
rather add the instruction and keep everything consistent.
-- 
Mike Kravetz

>  }
>  
>  void hugetlb_report_usage(struct seq_file *m, struct mm_struct *mm)
> @@ -3647,9 +3647,7 @@ static int hugetlb_vm_op_split(struct vm_area_struct *vma, unsigned long addr)
>  
>  static unsigned long hugetlb_vm_op_pagesize(struct vm_area_struct *vma)
>  {
> -	struct hstate *hstate = hstate_vma(vma);
> -
> -	return 1UL << huge_page_shift(hstate);
> +	return huge_page_size(hstate_vma(vma));
>  }
>  
>  /*
>