Messages in this thread | | | Date | Fri, 27 Jan 2023 16:48:23 -0800 | Subject | Re: [PATCH mm-unstable v2 1/6] mm: Add folio_estimated_mapcount() | From | Jane Chu <> |
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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
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