This will let us avoid an additional read from page->flags when
retrying the compare-exchange on some architectures.
Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Peter Collingbourne <[email protected]>
Link: https://linux-review.googlesource.com/id/I2e1f5b5b080ac9c4e0eb7f98768dba6fd7821693
---
mm/mmzone.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/mmzone.c b/mm/mmzone.c
index eb89d6e018e2..d8a9b0e1b526 100644
--- a/mm/mmzone.c
+++ b/mm/mmzone.c
@@ -89,13 +89,14 @@ int page_cpupid_xchg_last(struct page *page, int cpupid)
unsigned long old_flags, flags;
int last_cpupid;
+ old_flags = READ_ONCE(page->flags);
do {
- old_flags = flags = page->flags;
- last_cpupid = page_cpupid_last(page);
+ flags = old_flags;
+ last_cpupid = (flags >> LAST_CPUPID_PGSHIFT) & LAST_CPUPID_MASK;
flags &= ~(LAST_CPUPID_MASK << LAST_CPUPID_PGSHIFT);
flags |= (cpupid & LAST_CPUPID_MASK) << LAST_CPUPID_PGSHIFT;
- } while (unlikely(cmpxchg(&page->flags, old_flags, flags) != old_flags));
+ } while (unlikely(!try_cmpxchg(&page->flags, &old_flags, flags)));
return last_cpupid;
}
--
2.34.1.703.g22d0c6ccf7-goog