The patch titled Subject: Revert "mm: skip CMA pages when they are not available" has been added to the -mm mm-hotfixes-unstable branch. Its filename is revert-mm-skip-cma-pages-when-they-are-not-available.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Usama Arif usamaarif642@gmail.com Subject: Revert "mm: skip CMA pages when they are not available" Date: Wed, 21 Aug 2024 20:26:07 +0100

This reverts commit 5da226dbfce3a2f44978c2c7cf88166e69a6788b.

lruvec->lru_lock is highly contended and is held when calling isolate_lru_folios. If the lru has a large number of CMA folios consecutively, while the allocation type requested is not MIGRATE_MOVABLE, isolate_lru_folios can hold the lock for a very long time while it skips those. For FIO workload, ~150million order=0 folios were skipped to isolate a few ZONE_DMA folios [1]. This can cause lockups [1] and high memory pressure for extended periods of time [2].

[1] https://lore.kernel.org/all/CAOUHufbkhMZYz20aM_3rHZ3OcK4m2puji2FGpUpn_-DevGk... [2] https://lore.kernel.org/all/ZrssOrcJIDy8hacI@gmail.com/

Link: https://lkml.kernel.org/r/9060a32d-b2d7-48c0-8626-1db535653c54@gmail.com Fixes: 5da226dbfce3 ("mm: skip CMA pages when they are not available") Signed-off-by: Usama Arif usamaarif642@gmail.com Cc: Bharata B Rao bharata@amd.com Cc: Breno Leitao leitao@debian.org Cc: David Hildenbrand david@redhat.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Matthew Wilcox willy@infradead.org Cc: Rik van Riel riel@surriel.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Yu Zhao yuzhao@google.com Cc: Zhaoyang Huang huangzhaoyang@gmail.com Cc: Zhaoyang Huang zhaoyang.huang@unisoc.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/vmscan.c | 41 ++++++++++++++++++++--------------------- 1 file changed, 20 insertions(+), 21 deletions(-)

--- a/mm/vmscan.c~revert-mm-skip-cma-pages-when-they-are-not-available +++ a/mm/vmscan.c @@ -1604,25 +1604,6 @@ static __always_inline void update_lru_s

}

-#ifdef CONFIG_CMA -/* - * It is waste of effort to scan and reclaim CMA pages if it is not available - * for current allocation context. Kswapd can not be enrolled as it can not - * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL - */ -static bool skip_cma(struct folio *folio, struct scan_control *sc) -{ - return !current_is_kswapd() && - gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE && - folio_migratetype(folio) == MIGRATE_CMA; -} -#else -static bool skip_cma(struct folio *folio, struct scan_control *sc) -{ - return false; -} -#endif - /* * Isolating page from the lruvec to fill in @dst list by nr_to_scan times. * @@ -1669,8 +1650,7 @@ static unsigned long isolate_lru_folios( nr_pages = folio_nr_pages(folio); total_scan += nr_pages;

- if (folio_zonenum(folio) > sc->reclaim_idx || - skip_cma(folio, sc)) { + if (folio_zonenum(folio) > sc->reclaim_idx) { nr_skipped[folio_zonenum(folio)] += nr_pages; move_to = &folios_skipped; goto move; @@ -4273,6 +4253,25 @@ void lru_gen_soft_reclaim(struct mem_cgr

#endif /* CONFIG_MEMCG */

+#ifdef CONFIG_CMA +/* + * It is waste of effort to scan and reclaim CMA pages if it is not available + * for current allocation context. Kswapd can not be enrolled as it can not + * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL + */ +static bool skip_cma(struct folio *folio, struct scan_control *sc) +{ + return !current_is_kswapd() && + gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE && + folio_migratetype(folio) == MIGRATE_CMA; +} +#else +static bool skip_cma(struct folio *folio, struct scan_control *sc) +{ + return false; +} +#endif + /****************************************************************************** * the eviction ******************************************************************************/ _

Patches currently in -mm which might be from usamaarif642@gmail.com are

revert-mm-skip-cma-pages-when-they-are-not-available.patch