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Date: Thu, 17 Dec 2020 14:28:52 +0800 From: Alex Shi <alex.shi@...ux.alibaba.com> To: akpm@...ux-foundation.org Cc: Hugh Dickins <hughd@...gle.com>, Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: [PATCH 3/3] mm/compaction: remove rcu_read_lock during page compaction rcu_read_lock was used to guard memcg destory, now TestClearPageLRU could block this happen, so we don't need it. Remove it to reduce locking load in debugging mode. Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com> Cc: Hugh Dickins <hughd@...gle.com> Cc: Johannes Weiner <hannes@...xchg.org> Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: linux-mm@...ck.org Cc: linux-kernel@...r.kernel.org --- mm/compaction.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 8049d3530812..02af220fb992 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -995,7 +995,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, if (!TestClearPageLRU(page)) goto isolate_fail_put; - rcu_read_lock(); lruvec = mem_cgroup_page_lruvec(page, pgdat); /* If we already hold the lock, we can skip some rechecking */ @@ -1005,7 +1004,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, compact_lock_irqsave(&lruvec->lru_lock, &flags, cc); locked = lruvec; - rcu_read_unlock(); lruvec_memcg_debug(lruvec, page); @@ -1026,8 +1024,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, SetPageLRU(page); goto isolate_fail_put; } - } else - rcu_read_unlock(); + } /* The whole page is taken off the LRU; skip the tail pages. */ if (PageCompound(page)) -- 2.29.GIT
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