The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x bfe0857c20c663fcc1592fa4e3a61ca12b07dac9 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024090830-imaging-symphonic-8783@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

bfe0857c20c6 ("Revert "mm: skip CMA pages when they are not available"") 97144ce008f9 ("mm/vmscan: use folio_migratetype() instead of get_pageblock_migratetype()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bfe0857c20c663fcc1592fa4e3a61ca12b07dac9 Mon Sep 17 00:00:00 2001 From: Usama Arif usamaarif642@gmail.com Date: Wed, 21 Aug 2024 20:26:07 +0100 Subject: [PATCH] Revert "mm: skip CMA pages when they are not available"

This reverts commit 5da226dbfce3 ("mm: skip CMA pages when they are not available") and b7108d66318a ("Multi-gen LRU: skip CMA pages when they are not eligible").

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].

Remove skipping CMA for MGLRU as well, as it was introduced in sort_folio for the same resaon as 5da226dbfce3a2f44978c2c7cf88166e69a6788b.

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

[usamaarif642@gmail.com: also revert b7108d66318a, per Johannes] Link: https://lkml.kernel.org/r/9060a32d-b2d7-48c0-8626-1db535653c54@gmail.com Link: https://lkml.kernel.org/r/357ac325-4c61-497a-92a3-bdbd230d5ec9@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 Acked-by: Johannes Weiner hannes@cmpxchg.org Cc: Bharata B Rao bharata@amd.com Cc: Breno Leitao leitao@debian.org Cc: David Hildenbrand david@redhat.com 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

diff --git a/mm/vmscan.c b/mm/vmscan.c index cfa839284b92..bd489c1af228 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1604,25 +1604,6 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,

}

-#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(unsigned long nr_to_scan, 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; @@ -4320,7 +4300,7 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c }

/* ineligible */ - if (zone > sc->reclaim_idx || skip_cma(folio, sc)) { + if (zone > sc->reclaim_idx) { gen = folio_inc_gen(lruvec, folio, false); list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]); return true;