From: Ryan Roberts ryan.roberts@arm.com
next inclusion from next-20240510 commit 5ed890ce5147855c5360affd5e5419ed68a54100 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9OCYO CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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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.
Link: https://lkml.kernel.org/r/20240408183946.2991168-7-ryan.roberts@arm.com Signed-off-by: Ryan Roberts ryan.roberts@arm.com Reviewed-by: David Hildenbrand david@redhat.com Reviewed-by: Barry Song v-songbaohua@oppo.com Cc: Barry Song 21cnbao@gmail.com Cc: Chris Li chrisl@kernel.org Cc: Gao Xiang xiang@kernel.org Cc: "Huang, Ying" ying.huang@intel.com Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: Lance Yang ioworker0@gmail.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Michal Hocko mhocko@suse.com Cc: Yang Shi shy828301@gmail.com Cc: Yu Zhao yuzhao@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Liu Shixin liushixin2@huawei.com --- mm/vmscan.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c index 206be0d30d57..7e9cbb2bc454 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1903,25 +1903,25 @@ 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;