linux-kernel - Re: [RFC PATCH v2 9/9] mm: Introduce Copy-On-Write PTE table

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Message-ID: <YzQLMk5ViyoRIJUu@zhienlin-MBP>
Date:   Wed, 28 Sep 2022 16:52:02 +0800
From:   Chih-En Lin <shiyn.lin@...il.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Nadav Amit <namit@...are.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        William Kucharski <william.kucharski@...cle.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Peter Xu <peterx@...hat.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Tong Tiangen <tongtiangen@...wei.com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Li kunyu <kunyu@...china.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Minchan Kim <minchan@...nel.org>,
        Yang Shi <shy828301@...il.com>, Song Liu <song@...nel.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Dinglan Peng <peng301@...due.edu>,
        Pedro Fonseca <pfonseca@...due.edu>,
        Jim Huang <jserv@...s.ncku.edu.tw>,
        Huichun Feng <foxhoundsk.tw@...il.com>
Subject: Re: [RFC PATCH v2 9/9] mm: Introduce Copy-On-Write PTE table

On Tue, Sep 27, 2022 at 02:26:19PM -0700, John Hubbard wrote:
> On 9/27/22 12:53, Chih-En Lin wrote:
> > I'm not familiar with THP right now. But we have a plan for looking
> > at it to see what will happen with COW PTE.
> > Currently, I can only say that I prefer to avoid involving the behavior
> > of huge-page/THP. If there are any ideas here please tell us.
> > 
> In order to be considered at all, this would have to at least behave 
> correctly in the presence of THP and hugetlbfs, IMHO. Those are no
> longer niche features.
> 

To make sure it will work well with them. During fork() and page fault,
we put the mechanism after the hug-page/THP to make it doesn't mess up.
It may have corner cases that I didn't handle. I will keep looking at
it.

Thanks,
Chih-En lin