linux-kernel - Re: [PATCHv3, RESEND 8/8] khugepaged: Introduce 'max_ptes

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Message-ID: <20200416155206.bqpd5p45oud4chg6@box>
Date:   Thu, 16 Apr 2020 18:52:06 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        akpm@...ux-foundation.org, Andrea Arcangeli <aarcange@...hat.com>,
        Zi Yan <ziy@...dia.com>, Ralph Campbell <rcampbell@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        William Kucharski <william.kucharski@...cle.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3, RESEND 8/8] khugepaged: Introduce 'max_ptes_shared'
 tunable

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