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Date:   Thu, 16 Apr 2020 18:52:06 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Yang Shi <yang.shi@linux.alibaba.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        akpm@linux-foundation.org, Andrea Arcangeli <aarcange@redhat.com>,
        Zi Yan <ziy@nvidia.com>, Ralph Campbell <rcampbell@nvidia.com>,
        John Hubbard <jhubbard@nvidia.com>,
        William Kucharski <william.kucharski@oracle.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv3, RESEND 8/8] khugepaged: Introduce 'max_ptes_shared'
 tunable
Message-ID: <20200416155206.bqpd5p45oud4chg6@box>
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 <20200413125220.663-9-kirill.shutemov@linux.intel.com>
 <fcbfabac-1837-a4ea-1333-15445587e9fd@linux.alibaba.com>
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On Wed, Apr 15, 2020 at 02:25:30PM -0700, Yang Shi wrote:
> > @@ -595,6 +626,12 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> >   		VM_BUG_ON_PAGE(!PageAnon(page), page);
> > +		if (page_mapcount(page) > 1 &&
> > +				++shared > khugepaged_max_ptes_shared) {
> > +			result = SCAN_EXCEED_SHARED_PTE;
> 
> It may be better to extract the check into a helper? For example, bool
> exceed_max_ptes_shared(struct page)?

It might be reasonable as part of wider cleanup: the same has to be done
to khugepaged_max_ptes_none and khugepaged_max_ptes_swap.

Volunteers? :P

-- 
 Kirill A. Shutemov