mm: Remove unlikely from the current_order test
Subsystems (2)
PATCH 1/1 mm: Remove unlikely from the current_order test
From: Zhang Yanfei <[email protected]>
In __rmqueue_fallback(), current_order loops down from MAX_ORDER - 1 to the order passed. MAX_ORDER is typically 11 and pageblock_order is typically 9 on x86. Integer division truncates, so pageblock_order / 2 is 4. For the first eight iterations, it's guaranteed that current_order >= pageblock_order / 2 if it even gets that far!
So just remove the unlikely(), it's completely bogus.
--- mm/page_alloc.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
mm/page_alloc.c +1 -1
@@ -1050,7 +1050,7 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)* MIGRATE_CMA areas. */ if (!is_migrate_cma (migratetype) && - (unlikely (current_order >= pageblock_order /2 ) || + (current_order >= pageblock_order /2 || start_migratetype ==MIGRATE_RECLAIMABLE || page_group_by_mobility_disabled)) {int pages;
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Quoted 8 lines · Zhang Yanfei
From: Zhang Yanfei <[email protected]>
In
__rmqueue_fallback(),current_orderloops down fromMAX_ORDER- 1 to the order passed.MAX_ORDERis typically 11 andpageblock_orderis typically 9 on x86. Integer division truncates, sopageblock_order/ 2 is 4. For the first eight iterations, it's guaranteed thatcurrent_order>=pageblock_order/ 2 if it even gets that far!
Quoted 4 lines
So just remove the
unlikely(), it's completely bogus.Suggested-by David Rientjes <[email protected]>Signed-off-by Zhang Yanfei <[email protected]>
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