Messages in this thread | | | Date | Fri, 5 Apr 2024 12:42:35 +0200 | Subject | Re: [PATCH v6 5/6] mm: vmscan: Avoid split during shrink_folio_list() | From | David Hildenbrand <> |
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On 03.04.24 13:40, Ryan Roberts wrote: > Now that swap supports storing all mTHP sizes, avoid splitting large > folios before swap-out. This benefits performance of the swap-out path > by eliding split_folio_to_list(), which is expensive, and also sets us > up for swapping in large folios in a future series. > > If the folio is partially mapped, we continue to split it since we want > to avoid the extra IO overhead and storage of writing out pages > uneccessarily. > > THP_SWPOUT and THP_SWPOUT_FALLBACK counters should continue to count > events only for PMD-mappable folios to avoid user confusion. THP_SWPOUT > already has the appropriate guard. Add a guard for THP_SWPOUT_FALLBACK. > It may be appropriate to add per-size counters in future. > > Reviewed-by: David Hildenbrand <david@redhat.com> > Reviewed-by: Barry Song <v-songbaohua@oppo.com> > Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> > --- > mm/vmscan.c | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 00adaf1cb2c3..ffc4553c8615 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1223,11 +1223,12 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, > if (!can_split_folio(folio, NULL)) > goto activate_locked; > /* > - * Split folios without a PMD map right > - * away. Chances are some or all of the > - * tail pages can be freed without IO. > + * Split partially mapped folios right > + * away. We can free the unmapped pages > + * without IO. > */ > - if (!folio_entire_mapcount(folio) && > + if (data_race(!list_empty( > + &folio->_deferred_list)) &&
Please violate the 80 chars rule where reasonable.
" Statements longer than 80 columns should be broken into sensible chunks, unless exceeding 80 columns significantly increases readability and does not hide information. "
Likely some of that code here should be refactored into readable sub-functions.
codingstyle also mentions
"The answer to that is that if you need more than 3 levels of indentation, you're screwed anyway, and should fix your program."
-- Cheers,
David / dhildenb
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