Vlastimil Babka pointed out that an unlikely annotation in free_pages_prepare
shrinks stack usage by moving compound handling to the end of the function.
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-30 (-30)
function old new delta
free_pages_prepare 771 741 -30
It's also consistent with the buffered_rmqueue path.
This is a fix to the mmotm patch
mm-page_alloc-only-check-pagecompound-for-high-order-pages.patch.
Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1da56779f8fa..d8383750bd43 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1003,7 +1003,7 @@ static bool free_pages_prepare(struct page *page, unsigned int order)
* Check tail pages before head page information is cleared to
* avoid checking PageCompound for order-0 pages.
*/
- if (order) {
+ if (unlikely(order)) {
bool compound = PageCompound(page);
int i;
--
2.6.4
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