From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Shi Subject: [PATCH v2 6/8] mm/lru: remove rcu_read_lock to fix performance regression Date: Tue, 12 Nov 2019 22:06:26 +0800 Message-ID: <1573567588-47048-7-git-send-email-alex.shi@linux.alibaba.com> References: <1573567588-47048-1-git-send-email-alex.shi@linux.alibaba.com> Return-path: In-Reply-To: <1573567588-47048-1-git-send-email-alex.shi@linux.alibaba.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: alex.shi@linux.alibaba.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@techsingularity.net, tj@kernel.org, hughd@google.com, khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com, yang.shi@linux.alibaba.com Cc: Johannes Weiner , Roman Gushchin , Shakeel Butt , Chris Down , Thomas Gleixner Intel 0day report there are performance regression on this patchset. The detailed info points to rcu_read_lock + PROVE_LOCKING which causes queued_spin_lock_slowpath waiting too long time to get lock. Remove rcu_read_lock is safe here since we had a spinlock hold. Reported-by: kbuild test robot Signed-off-by: Alex Shi Cc: Andrew Morton Cc: Johannes Weiner Cc: Roman Gushchin Cc: Shakeel Butt Cc: Chris Down Cc: Tejun Heo Cc: Thomas Gleixner Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- include/linux/memcontrol.h | 29 ++++++++++++----------------- 1 file changed, 12 insertions(+), 17 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 2421b720d272..f869897a68f0 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1307,20 +1307,18 @@ static inline struct lruvec *relock_page_lruvec_irq(struct page *page, struct pglist_data *pgdat = page_pgdat(page); struct lruvec *lruvec; - rcu_read_lock(); + if (!locked_lruvec) + goto lock; + lruvec = mem_cgroup_page_lruvec(page, pgdat); - if (locked_lruvec == lruvec) { - rcu_read_unlock(); + if (locked_lruvec == lruvec) return lruvec; - } - rcu_read_unlock(); - if (locked_lruvec) - spin_unlock_irq(&locked_lruvec->lru_lock); + spin_unlock_irq(&locked_lruvec->lru_lock); +lock: lruvec = lock_page_lruvec_irq(page, pgdat); - return lruvec; } @@ -1331,21 +1329,18 @@ static inline struct lruvec *relock_page_lruvec_irqsave(struct page *page, struct pglist_data *pgdat = page_pgdat(page); struct lruvec *lruvec; - rcu_read_lock(); + if (!locked_lruvec) + goto lock; + lruvec = mem_cgroup_page_lruvec(page, pgdat); - if (locked_lruvec == lruvec) { - rcu_read_unlock(); + if (locked_lruvec == lruvec) return lruvec; - } - rcu_read_unlock(); - if (locked_lruvec) - spin_unlock_irqrestore(&locked_lruvec->lru_lock, - locked_lruvec->flags); + spin_unlock_irqrestore(&locked_lruvec->lru_lock, locked_lruvec->flags); +lock: lruvec = lock_page_lruvec_irqsave(page, pgdat); - return lruvec; } -- 1.8.3.1