The patch titled
Subject: mm/page_alloc: remove unnecessary page == NULL check in rmqueue
has been added to the -mm mm-unstable branch. Its filename is
mm-page_alloc-remove-unnecessary-page-==-null-check-in-rmqueue.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-remove-unnecessary-page-==-null-check-in-rmqueue.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: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm/page_alloc: remove unnecessary page == NULL check in rmqueue
The VM_BUG_ON check for a valid page can be avoided with a simple change
in the flow. The ZONE_BOOSTED_WATERMARK is unlikely in general and even
more unlikely if the page allocation failed so mark the branch unlikely.
Link: https://lkml.kernel.org/r/20220512085043.5234-5-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Tested-by: Minchan Kim <minchan@xxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Nicolas Saenz Julienne <nsaenzju@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-remove-unnecessary-page-==-null-check-in-rmqueue
+++ a/mm/page_alloc.c
@@ -3755,17 +3755,18 @@ struct page *rmqueue(struct zone *prefer
page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
migratetype);
- if (unlikely(!page))
- return NULL;
out:
/* Separate test+clear to avoid unnecessary atomics */
- if (test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags)) {
+ if (unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
wakeup_kswapd(zone, 0, 0, zone_idx(zone));
}
- VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
+ if (unlikely(!page))
+ return NULL;
+
+ VM_BUG_ON_PAGE(bad_range(zone, page), page);
return page;
}
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-page_alloc-add-page-buddy_list-and-page-pcp_list.patch
mm-page_alloc-use-only-one-pcp-list-for-thp-sized-allocations.patch
mm-page_alloc-split-out-buddy-removal-code-from-rmqueue-into-separate-helper.patch
mm-page_alloc-remove-unnecessary-page-==-null-check-in-rmqueue.patch
mm-page_alloc-protect-pcp-lists-with-a-spinlock.patch
