From: Jane Chu <jane.chu@oracle.com>
To: David Hildenbrand <david@redhat.com>,
Vishal Moola <vishal.moola@gmail.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH mm-unstable v2 1/6] mm: Add folio_estimated_mapcount()
Date: Fri, 27 Jan 2023 16:48:23 -0800 [thread overview]
Message-ID: <3a6af06a-729d-7659-50b0-8b242b555134@oracle.com> (raw)
In-Reply-To: <52af321f-175b-9fa9-10f0-ac2bba04c677@redhat.com>
On 1/26/2023 12:37 AM, David Hildenbrand wrote:
> On 25.01.23 23:09, Vishal Moola wrote:
[..]
>
> The issue is that we're not estimating the mapcount of the folio, so the
> name is very misleading ... I think you really want to avoid the term
> mapcount completely in that context. We're just using the #mappings of
> the first subpage to determine something differently.
>
> Thinking about it, I guess "folio_estimated_sharers()" might be what we
> actually want to name it. Then you can comment how we estimate sharers
> by looking at into how many page tables the first subpage is currently
> mapped, and assume the same holds true for the other subpages.
>
> It's unreliable because other subpages might behave differently, we
> might not be holding the pagelock to stabilize, and we're not looking at
> indirect mappings via the swapcache. But it's a comapratively good
> estimate for most scenarios I guess.
>
Hmm, how about simply call it folio_hpage_mapcount(),
folio_firstpage_mapcount(), or, folio_cover_mapcount() ?
It is used to replace page_mapcount() in that sense -
https://lore.kernel.org/linux-mm/Y9MDJuPWsk9820xD@x1n/T/#me0531cfb9e82ad5ca88804c727d69cc6b9b33ffa
if (flags & (MPOL_MF_MOVE_ALL) ||
(flags & MPOL_MF_MOVE && folio_estimated_mapcount(folio) == 1 &&
!hugetlb_pmd_shared(pte))) {
if (isolate_hugetlb(folio, qp->pagelist) &&
thanks,
-jane
next prev parent reply other threads:[~2023-01-28 0:49 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-24 1:22 [PATCH mm-unstable v2 0/6] Convert various mempolicy.c functions Vishal Moola (Oracle)
2023-01-24 1:22 ` [PATCH mm-unstable v2 1/6] mm: Add folio_estimated_mapcount() Vishal Moola (Oracle)
2023-01-24 3:23 ` kernel test robot
2023-01-25 10:20 ` David Hildenbrand
2023-01-25 10:24 ` David Hildenbrand
2023-01-25 21:29 ` David Hildenbrand
2023-01-25 22:09 ` Vishal Moola
2023-01-26 8:37 ` David Hildenbrand
2023-01-28 0:48 ` Jane Chu [this message]
2023-01-30 9:34 ` David Hildenbrand
2023-01-28 13:20 ` Yin, Fengwei
2023-01-24 1:22 ` [PATCH mm-unstable v2 2/6] mm/mempolicy: Convert queue_pages_pmd() to queue_folios_pmd() Vishal Moola (Oracle)
2023-01-24 1:22 ` [PATCH mm-unstable v2 3/6] mm/mempolicy: Convert queue_pages_pte_range() to queue_folios_pte_range() Vishal Moola (Oracle)
2023-01-24 1:22 ` [PATCH mm-unstable v2 4/6] mm/mempolicy: Convert queue_pages_hugetlb() to queue_folios_hugetlb() Vishal Moola (Oracle)
2023-01-24 1:22 ` [PATCH mm-unstable v2 5/6] mm/mempolicy: Convert queue_pages_required() to queue_folio_required() Vishal Moola (Oracle)
2023-01-24 1:22 ` [PATCH mm-unstable v2 6/6] mm/mempolicy: Convert migrate_page_add() to migrate_folio_add() Vishal Moola (Oracle)
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