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

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Date:   Mon, 8 Feb 2021 17:36:40 -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 5:24 PM, Miaohe Lin wrote:
> Hi：
> On 2021/2/9 8:45, Mike Kravetz wrote:
>> 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.
>>
> 
> Yes, it takes an additional instruction to do the divide as opposed to the shift. So I did not
> change this. But it seems keeping everything consistent in a function is more important. So should
> I send a V2 to change this or Andrew would kindly handle this ?

I would go ahead and put together a v2 and let Andrew decide how he wants
to handle it.  You can include,

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>

Thanks
-- 
Mike Kravetz