The patch titled
Subject: mm: thp: update split_queue_len correctly
has been added to the -mm tree. Its filename is
mm-thp-update-split_queue_len-correctly.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-thp-update-split_queue_len-correctly.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-update-split_queue_len-correctly.patch
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------------------------------------------------------
From: Shakeel Butt <shakeelb@xxxxxxxxxx>
Subject: mm: thp: update split_queue_len correctly
The deferred THPs are split on memory pressure through shrinker callback
and splitting of THP during reclaim can fail for several reasons like
unable to lock the THP, under writeback or unexpected number of pins on
the THP. Such pages are put back on the deferred split list for
consideration later. However kernel does not update the deferred queue
size on putting back the pages whose split was failed. This patch fixes
that.
Without this patch the split_queue_len can underflow. Shrinker will
always get that there are some THPs to split even if there are not and
waste some cpu to scan the empty list.
Link: https://lkml.kernel.org/r/20211123190916.1738458-1-shakeelb@xxxxxxxxxx
Fixes: 364c1eebe453 ("mm: thp: extract split_queue_* into a struct")
Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/huge_memory.c~mm-thp-update-split_queue_len-correctly
+++ a/mm/huge_memory.c
@@ -2809,7 +2809,7 @@ static unsigned long deferred_split_scan
unsigned long flags;
LIST_HEAD(list), *pos, *next;
struct page *page;
- int split = 0;
+ unsigned long split = 0;
#ifdef CONFIG_MEMCG
if (sc->memcg)
@@ -2847,6 +2847,7 @@ next:
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
list_splice_tail(&list, &ds_queue->split_queue);
+ ds_queue->split_queue_len -= split;
spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
/*
_
Patches currently in -mm which might be from shakeelb@xxxxxxxxxx are
memcg-better-bounds-on-the-memcg-stats-updates.patch
mm-thp-update-split_queue_len-correctly.patch
