linux-kernel - Re: [RFC PATCH 10/26] hugetlb: add for_each_hgm

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Message-ID: <285ac7f8-20f2-c260-90e2-6271ecddaf73@nutanix.com>
Date:   Mon, 27 Jun 2022 18:31:39 +0530
From:   "manish.mishra" <manish.mishra@...anix.com>
To:     James Houghton <jthoughton@...gle.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Peter Xu <peterx@...hat.com>
Cc:     David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Jue Wang <juew@...gle.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 10/26] hugetlb: add for_each_hgm_shift


On 24/06/22 11:06 pm, James Houghton wrote:
> This is a helper macro to loop through all the usable page sizes for a
> high-granularity-enabled HugeTLB VMA. Given the VMA's hstate, it will
> loop, in descending order, through the page sizes that HugeTLB supports
> for this architecture; it always includes PAGE_SIZE.
reviewed-by:manish.mishra@...anix.com
> Signed-off-by: James Houghton <jthoughton@...gle.com>
> ---
>   mm/hugetlb.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 8b10b941458d..557b0afdb503 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6989,6 +6989,16 @@ bool hugetlb_hgm_enabled(struct vm_area_struct *vma)
>   	/* All shared VMAs have HGM enabled. */
>   	return vma->vm_flags & VM_SHARED;
>   }
> +static unsigned int __shift_for_hstate(struct hstate *h)
> +{
> +	if (h >= &hstates[hugetlb_max_hstate])
> +		return PAGE_SHIFT;
> +	return huge_page_shift(h);
> +}
> +#define for_each_hgm_shift(hstate, tmp_h, shift) \
> +	for ((tmp_h) = hstate; (shift) = __shift_for_hstate(tmp_h), \
> +			       (tmp_h) <= &hstates[hugetlb_max_hstate]; \
> +			       (tmp_h)++)
>   #endif /* CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING */
>   
>   /*