linux-kernel - Re: [PATCH v1] mm: convert folio_estimated_sharers() to folio_likely_mapped

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Date: Thu, 29 Feb 2024 10:28:50 -0500
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Barry Song <v-songbaohua@...o.com>, Vishal Moola <vishal.moola@...il.com>,
 Ryan Roberts <ryan.roberts@....com>
Subject: Re: [PATCH v1] mm: convert folio_estimated_sharers() to
 folio_likely_mapped_shared()

On 27 Feb 2024, at 15:15, David Hildenbrand wrote:

> Callers of folio_estimated_sharers() only care about "mapped shared vs.
> mapped exclusively", not the exact estimate of sharers. Let's consolidate
> and unify the condition users are checking. While at it clarify the
> semantics and extend the discussion on the fuzziness.
>
> Use the "likely mapped shared" terminology to better express what the
> (adjusted) function actually checks.
>
> Whether a partially-mappable folio is more likely to not be partially
> mapped than partially mapped is debatable. In the future, we might be able
> to improve our estimate for partially-mappable folios, though.
>
> Note that we will now consistently detect "mapped shared" only if the
> first subpage is actually mapped multiple times. When the first subpage
> is not mapped, we will consistently detect it as "mapped exclusively".
> This change should currently only affect the usage in
> madvise_free_pte_range() and queue_folios_pte_range() for large folios: if
> the first page was already unmapped, we would have skipped the folio.
>
> Cc: Barry Song <v-songbaohua@...o.com>
> Cc: Vishal Moola (Oracle) <vishal.moola@...il.com>
> Cc: Ryan Roberts <ryan.roberts@....com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
LGTM. Thanks for the documentation. Reviewed-by: Zi Yan <ziy@...dia.com>

--
Best Regards,
Yan, Zi

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