From: Yang Shi <shy828301@gmail.com>
To: Peter Xu <peterx@redhat.com>
Cc: David Stevens <stevensd@chromium.org>,
David Hildenbrand <david@redhat.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH] mm/khugepaged: skip shmem with armed userfaultfd
Date: Thu, 2 Feb 2023 13:11:22 -0800 [thread overview]
Message-ID: <CAHbLzkrYEOD6-35kjGeS6ftXJ_mfzugwLt_28n+hH3Vy-uBs3g@mail.gmail.com> (raw)
In-Reply-To: <Y9wXXoSY+QqoKMMx@x1n>
On Thu, Feb 2, 2023 at 12:04 PM Peter Xu <peterx@redhat.com> wrote:
>
> On Wed, Feb 01, 2023 at 03:57:33PM -0800, Yang Shi wrote:
> > > There's another problem where the current vma may not have uffd armed,
> > > khugepaged may think it has nothing to do with uffd and moved on with
> > > collapsing, but actually it's armed in another vma of either the current mm
> > > or just another mm's.
> >
> > Out of curiosity, could you please elaborate how another vma armed
> > with userfaultfd could have an impact on the vmas that are not armed?
>
> It's e.g. when >1 vmas mapped to the same shmem file on the same range, one
> registered with uffd missing, others not. Then others can cause page cache
> populated without generating message to the vma that got uffd missing mode
> registered, so there'll be the same issue as when khugepaged accidentally
> does thp collapsings. Thanks,
Got it, thank you.
>
> --
> Peter Xu
>
next prev parent reply other threads:[~2023-02-02 21:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 3:41 David Stevens
2023-02-01 17:36 ` Yang Shi
2023-02-01 20:52 ` Peter Xu
2023-02-01 23:57 ` Yang Shi
2023-02-02 20:04 ` Peter Xu
2023-02-02 21:11 ` Yang Shi [this message]
2023-02-02 9:56 ` David Stevens
2023-02-02 17:40 ` Yang Shi
2023-02-02 20:22 ` Peter Xu
2023-02-03 6:09 ` David Stevens
2023-02-03 14:56 ` Peter Xu
2023-02-01 23:09 ` Kirill A. Shutemov
2023-02-02 9:30 ` David Stevens
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