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mm/mmzone.c: use try_cmpxchg() in page_cpupid_xchg_last()

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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>
This commit is contained in:
Peter Collingbourne 2022-03-22 14:43:08 -07:00 committed by Linus Torvalds
parent 1dd214b8f2
commit abe8b2ae64
1 changed files with 4 additions and 3 deletions
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7
mm/mmzone.c
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@ -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;
}