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Message-Id: <8FBBFD68-3315-48D6-B318-4AA5A170C0C8@gmail.com>
Date: Thu, 4 Aug 2022 15:17:44 -0700
From: Nadav Amit <nadav.amit@...il.com>
To: Peter Xu <peterx@...hat.com>
Cc: Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
Huang Ying <ying.huang@...el.com>,
Andrea Arcangeli <aarcange@...hat.com>,
David Hildenbrand <david@...hat.com>,
Minchan Kim <minchan@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Vlastimil Babka <vbabka@...e.cz>,
Hugh Dickins <hughd@...gle.com>,
Andi Kleen <andi.kleen@...el.com>,
"Kirill A . Shutemov" <kirill@...temov.name>
Subject: Re: [PATCH v2 0/2] mm: Remember a/d bits for migration entries
On Aug 4, 2022, at 1:39 PM, Peter Xu <peterx@...hat.com> wrote:
> (1) Page Idle Tracking
>
> Before this series, idle tracking can cause false negative if an accessed
> page got migrated, since after migration the young bit will get lost.
> After this series, it'll be better in that after migration young bit will
> be persisted, so it'll be able to be detected correctly by page idle
> logic when walking the pgtable.
>
> However there's still nothing done when page idle reset was carried out
> during migration procedure in progress, but that should be a separate
> topic to be addressed (e.g. to teach rmap pgtable walk code to be able to
> walk with both present ptes and migration ptes).
IIUC, when a migration entry is set page_remove_rmap() is called by
try_to_migrate_one(), so improving page-idle accuracy should be done in a
different way.
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