linux-kernel - Re: [PATCHv3, RESEND 6/8] khugepaged: Allow to collapse PTE-mapped compound pages

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Message-Id: <20200415155259.8be9887c64b1420cfc9b9655@linux-foundation.org>
Date:   Wed, 15 Apr 2020 15:52:59 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Zi Yan <ziy@...dia.com>, Yang Shi <yang.shi@...ux.alibaba.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 6/8] khugepaged: Allow to collapse PTE-mapped
 compound pages

On Thu, 16 Apr 2020 00:52:05 +0300 "Kirill A. Shutemov" <kirill@...temov.name> wrote:

> On Wed, Apr 15, 2020 at 02:44:26PM -0700, Andrew Morton wrote:
> > On Mon, 13 Apr 2020 15:52:18 +0300 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> wrote:
> > 
> > > We can collapse PTE-mapped compound pages. We only need to avoid
> > > handling them more than once: lock/unlock page only once if it's present
> > > in the PMD range multiple times as it handled on compound level. The
> > > same goes for LRU isolation and putback.
> > > 
> > > ...
> > >
> > > --- a/mm/khugepaged.c
> > > +++ b/mm/khugepaged.c
> > > @@ -515,17 +515,30 @@ void __khugepaged_exit(struct mm_struct *mm)
> > >  
> > >  static void release_pte_page(struct page *page)
> > >  {
> > > -	dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
> > 
> > I have
> > 
> > 	dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_lru(page));
> > 
> > here.  Is there some prerequisite which I wasn't able to find?
> 
> The patchset is on top of v5.6. It has been changed since. See
> 9de4f22a60f7 ("mm: code cleanup for MADV_FREE").
> 
> Look like a trivial fixup is required.

[7/8] makes a big mess.  Can we please have a v4?