| From: Mel Gorman <mgorman@techsingularity.net> |
| 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@techsingularity.net |
| Signed-off-by: Mel Gorman <mgorman@techsingularity.net> |
| Tested-by: Minchan Kim <minchan@kernel.org> |
| Acked-by: Minchan Kim <minchan@kernel.org> |
| Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com> |
| Cc: Marcelo Tosatti <mtosatti@redhat.com> |
| Cc: Michal Hocko <mhocko@kernel.org> |
| Cc: Vlastimil Babka <vbabka@suse.cz> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| 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 |
| @@ -3752,17 +3752,18 @@ 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; |
| } |
| |
| _ |
