linux-kernel - Re: [PATCH] proc: mm: export PTE sizes directly in smaps (v3)

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Date:   Fri, 02 Dec 2016 21:44:57 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:     Dave Hansen <dave@...1.net>, linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave@...1.net>, hch@....de, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, khandual@...ux.vnet.ibm.com,
        vbabka@...e.cz, linux-mm@...ck.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH] proc: mm: export PTE sizes directly in smaps (v3)

Dave Hansen <dave@...1.net> writes:

  
>  #ifdef CONFIG_HUGETLB_PAGE
> +/*
> + * Most architectures have a 1:1 mapping of PTEs to hugetlb page
> + * sizes, but there are some outliers like arm64 that use
> + * multiple hardware PTEs to make a hugetlb "page".  Do not
> + * assume that all 'hpage_size's are not exactly at a page table
> + * size boundary.  Instead, accept arbitrary 'hpage_size's and
> + * assume they are made up of the next-smallest size.  We do not
> + * handle PGD-sized hpages and hugetlb_add_hstate() will WARN()
> + * if it sees one.
> + *
> + * Note also that the page walker code only calls us once per
> + * huge 'struct page', *not* once per PTE in the page tables.
> + */
> +static void smaps_hugetlb_present_hpage(struct mem_size_stats *mss,
> +					unsigned long hpage_size)
> +{
> +	if (hpage_size >= PUD_SIZE)
> +		mss->rss_pud += hpage_size;
> +	else if (hpage_size >= PMD_SIZE)
> +		mss->rss_pmd += hpage_size;
> +	else
> +		mss->rss_pte += hpage_size;
> +}

some powerpc platforms have multiple page table entries mapping the same
hugepage and on other, we have a page table entry pointing to something
called hugepaeg directory mapping a set of hugepage. So I am not sure
the above will work for all those ?

Also do we derive pte@<size value> correctly there ?

-aneesh