This will let us avoid an additional read from page->flags when retrying the compare-exchange on some architectures. Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> 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
