Commit 05d45a37 authored by Ryan Roberts's avatar Ryan Roberts Committed by Liu Shixin
Browse files

mm: vmscan: avoid split during shrink_folio_list() 

next inclusion
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/?id=5ed890ce5147855c5360affd5e5419ed68a54100

--------------------------------

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: default avatarRyan Roberts <ryan.roberts@arm.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarBarry 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent 98829570

mm/vmscan.c

+10 −10
Original line number Diff line number Diff line
@@ -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);

					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;