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authorPeter Collingbourne <pcc@google.com>2022-03-22 14:43:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-22 15:57:05 -0700
commitabe8b2ae64a31146748239a1525ffb275c4f360f (patch)
tree31ddaf821a71ee2a11a4dbb0caa40a58e5e3fd5e /mm/mmzone.c
parent1dd214b8f21ca46d5431be9b2db8513c59e07a26 (diff)
mm/mmzone.c: use try_cmpxchg() in page_cpupid_xchg_last()
This will let us avoid an additional read from page->flags when retrying the compare-exchange on some architectures. Link: https://lkml.kernel.org/r/20220120011200.1322836-1-pcc@google.com Link: https://linux-review.googlesource.com/id/I2e1f5b5b080ac9c4e0eb7f98768dba6fd7821693 Signed-off-by: Peter Collingbourne <pcc@google.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmzone.c')
-rw-r--r--mm/mmzone.c7
1 files 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;
}