Messages in this thread | | | Date | Wed, 9 Aug 2023 17:23:46 -0400 | From | Peter Xu <> | Subject | Re: [PATCH mm-unstable v1] mm: add a total mapcount for large folios |
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Hi, David,
Some pure questions below..
On Wed, Aug 09, 2023 at 10:32:56AM +0200, David Hildenbrand wrote: > Let's track the total mapcount for all large folios in the first subpage. > > The total mapcount is what we actually want to know in folio_mapcount() > and it is also sufficient for implementing folio_mapped(). This also > gets rid of any "raceiness" concerns as expressed in > folio_total_mapcount().
Any more information for that "raciness" described here?
> > With sub-PMD THP becoming more important and things looking promising > that we will soon get support for such anon THP, we want to avoid looping > over all pages of a folio just to calculate the total mapcount. Further, > we may soon want to use the total mapcount in other context more > frequently, so prepare for reading it efficiently and atomically.
Any (perhaps existing) discussion on reduced loops vs added atomic field/ops?
I had a feeling that there's some discussion behind the proposal of this patch, if that's the case it'll be great to attach the link in the commit log.
Thanks,
-- Peter Xu
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