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mm: swap: use smp_mb__after_atomic() to order LRU bit set

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Memory barrier is needed after setting LRU bit, but smp_mb() is too
strong.  Some architectures, i.e.  x86, imply memory barrier with atomic
operations, so replacing it with smp_mb__after_atomic() sounds better,
which is nop on strong ordered machines, and full memory barriers on
others.  With this change the vm-scalability cases would perform better on
x86, I saw total 6% improvement with this patch and previous inline fix.

The test data (lru-file-readtwice throughput) against v5.6-rc4:
	mainline	w/ inline fix	w/ both (adding this)
	150MB		154MB		159MB

Fixes: 9c4e6b1a70 ("mm, mlock, vmscan: no more skipping pagevecs")
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: http://lkml.kernel.org/r/1584500541-46817-2-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yang Shi 2020-04-01 21:06:23 -07:00 committed by Linus Torvalds
parent 1eb6234e52
commit 9a9b6cce63
1 changed files with 2 additions and 2 deletions
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4
mm/swap.c
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@ -931,7 +931,6 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
VM_BUG_ON_PAGE(PageLRU(page), page);
SetPageLRU(page);
/*
* Page becomes evictable in two ways:
* 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()].
@ -958,7 +957,8 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
* looking at the same page) and the evictable page will be stranded
* in an unevictable LRU.
*/
smp_mb();
SetPageLRU(page);
smp_mb__after_atomic();
if (page_evictable(page)) {
lru = page_lru(page);