+ mm-skip-cma-pages-when-they-are-not-available.patch added to mm-unstable branch

+ mm-skip-cma-pages-when-they-are-not-available.patch added to mm-unstable branch

[Andrew Morton]

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

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

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------------------------------------------------------
From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
Subject: mm: skip CMA pages when they are not available
Date: Wed, 31 May 2023 10:51:01 +0800

This patch fixes unproductive reclaiming of CMA pages by skipping them
when they are not available for current context.  It arises from the below
OOM issue, which was caused by a large proportion of MIGRATE_CMA pages
among free pages.

[   36.172486] [03-19 10:05:52.172] ActivityManager: page allocation failure: order:0, mode:0xc00(GFP_NOIO), nodemask=(null),cpuset=foreground,mems_allowed=0
[   36.189447] [03-19 10:05:52.189] DMA32: 0*4kB 447*8kB (C) 217*16kB (C) 124*32kB (C) 136*64kB (C) 70*128kB (C) 22*256kB (C) 3*512kB (C) 0*1024kB 0*2048kB 0*4096kB = 35848kB
[   36.193125] [03-19 10:05:52.193] Normal: 231*4kB (UMEH) 49*8kB (MEH) 14*16kB (H) 13*32kB (H) 8*64kB (H) 2*128kB (H) 0*256kB 1*512kB (H) 0*1024kB 0*2048kB 0*4096kB = 3236kB
...
[   36.234447] [03-19 10:05:52.234] SLUB: Unable to allocate memory on node -1, gfp=0xa20(GFP_ATOMIC)
[   36.234455] [03-19 10:05:52.234] cache: ext4_io_end, object size: 64, buffer size: 64, default order: 0, min order: 0
[   36.234459] [03-19 10:05:52.234] node 0: slabs: 53,objs: 3392, free: 0

Link: https://lkml.kernel.org/r/1685501461-19290-1-git-send-email-zhaoyang.huang@unisoc.com
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
Cc: ke.wang <ke.wang@unisoc.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |   22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

--- a/mm/vmscan.c~mm-skip-cma-pages-when-they-are-not-available
+++ a/mm/vmscan.c
@@ -2271,6 +2271,25 @@ 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 &&
+			get_pageblock_migratetype(&folio->page) == 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.
  *
@@ -2317,7 +2336,8 @@ static unsigned long isolate_lru_folios(
 		nr_pages = folio_nr_pages(folio);
 		total_scan += nr_pages;
 
-		if (folio_zonenum(folio) > sc->reclaim_idx) {
+		if (folio_zonenum(folio) > sc->reclaim_idx ||
+				skip_cma(folio, sc)) {
 			nr_skipped[folio_zonenum(folio)] += nr_pages;
 			move_to = &folios_skipped;
 			goto move;
_

Patches currently in -mm which might be from zhaoyang.huang@unisoc.com are

mm-optimization-on-page-allocation-when-cma-enabled.patch
mm-skip-cma-pages-when-they-are-not-available.patch