Messages in this thread Patch in this message | | | From | Ryan Roberts <> | Subject | [PATCH v7 6/7] mm: vmscan: Avoid split during shrink_folio_list() | Date | Mon, 8 Apr 2024 19:39:45 +0100 |
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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 | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c index 00adaf1cb2c3..bca2d9981c95 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1223,25 +1223,25 @@ 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) && - split_folio_to_list(folio, - folio_list)) + if (data_race(!list_empty(&folio->_deferred_list)) && + split_folio_to_list(folio, folio_list)) goto activate_locked; } if (!add_to_swap(folio)) { if (!folio_test_large(folio)) goto activate_locked_split; /* Fallback to swap normal pages */ - if (split_folio_to_list(folio, - folio_list)) + if (split_folio_to_list(folio, folio_list)) goto activate_locked; #ifdef CONFIG_TRANSPARENT_HUGEPAGE - count_memcg_folio_events(folio, THP_SWPOUT_FALLBACK, 1); - count_vm_event(THP_SWPOUT_FALLBACK); + if (nr_pages >= HPAGE_PMD_NR) { + count_memcg_folio_events(folio, + THP_SWPOUT_FALLBACK, 1); + count_vm_event(THP_SWPOUT_FALLBACK); + } #endif if (!add_to_swap(folio)) goto activate_locked_split; -- 2.25.1
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