From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C750C433DF for ; Fri, 31 Jul 2020 23:55:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D4872054F for ; Fri, 31 Jul 2020 23:55:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727940AbgGaXzE (ORCPT ); Fri, 31 Jul 2020 19:55:04 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:40170 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726099AbgGaXzE (ORCPT ); Fri, 31 Jul 2020 19:55:04 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04357;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=22;SR=0;TI=SMTPD_---0U4Ln6pe_1596239697; Received: from IT-FVFX43SYHV2H.lan(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0U4Ln6pe_1596239697) by smtp.aliyun-inc.com(127.0.0.1); Sat, 01 Aug 2020 07:54:59 +0800 Subject: Re: [PATCH RFC] mm: Add function for testing if the current lruvec lock is valid To: alexander.h.duyck@intel.com Cc: akpm@linux-foundation.org, alexander.duyck@gmail.com, aryabinin@virtuozzo.com, cgroups@vger.kernel.org, daniel.m.jordan@oracle.com, hannes@cmpxchg.org, hughd@google.com, iamjoonsoo.kim@lge.com, khlebnikov@yandex-team.ru, kirill@shutemov.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lkp@intel.com, mgorman@techsingularity.net, richard.weiyang@gmail.com, rong.a.chen@intel.com, shakeelb@google.com, tglx@linutronix.de, tj@kernel.org, willy@infradead.org, yang.shi@linux.alibaba.com References: <1595681998-19193-19-git-send-email-alex.shi@linux.alibaba.com> <159622999150.2576729.14455020813024958573.stgit@ahduyck-desk1.jf.intel.com> From: Alex Shi Message-ID: <0c0a415a-52a0-5c06-b4be-80cbd3cb49c2@linux.alibaba.com> Date: Sat, 1 Aug 2020 07:54:48 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <159622999150.2576729.14455020813024958573.stgit@ahduyck-desk1.jf.intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It looks much better than mine. and could replace 'mm/lru: introduce the relock_page_lruvec function' with your author signed. :) BTW, it's the rcu_read_lock cause the will-it-scale/page_fault3 regression which you mentained in another letter? Thanks Alex 在 2020/8/1 上午5:14, alexander.h.duyck@intel.com 写道: > From: Alexander Duyck > > When testing for relock we can avoid the need for RCU locking if we simply > compare the page pgdat and memcg pointers versus those that the lruvec is > holding. By doing this we can avoid the extra pointer walks and accesses of > the memory cgroup. > > In addition we can avoid the checks entirely if lruvec is currently NULL. > > Signed-off-by: Alexander Duyck > --- > include/linux/memcontrol.h | 52 +++++++++++++++++++++++++++----------------- > 1 file changed, 32 insertions(+), 20 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 6e670f991b42..7a02f00bf3de 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -405,6 +405,22 @@ static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg, > > struct lruvec *mem_cgroup_page_lruvec(struct page *, struct pglist_data *); > > +static inline bool lruvec_holds_page_lru_lock(struct page *page, > + struct lruvec *lruvec) > +{ > + pg_data_t *pgdat = page_pgdat(page); > + const struct mem_cgroup *memcg; > + struct mem_cgroup_per_node *mz; > + > + if (mem_cgroup_disabled()) > + return lruvec == &pgdat->__lruvec; > + > + mz = container_of(lruvec, struct mem_cgroup_per_node, lruvec); > + memcg = page->mem_cgroup ? : root_mem_cgroup; > + > + return lruvec->pgdat == pgdat && mz->memcg == memcg; > +} > + > struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p); > > struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm); > @@ -880,6 +896,14 @@ static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page, > return &pgdat->__lruvec; > } > > +static inline bool lruvec_holds_page_lru_lock(struct page *page, > + struct lruvec *lruvec) > +{ > + pg_data_t *pgdat = page_pgdat(page); > + > + return lruvec == &pgdat->__lruvec; > +} > + > static inline struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg) > { > return NULL; > @@ -1317,18 +1341,12 @@ static inline void unlock_page_lruvec_irqrestore(struct lruvec *lruvec, > static inline struct lruvec *relock_page_lruvec_irq(struct page *page, > struct lruvec *locked_lruvec) > { > - struct pglist_data *pgdat = page_pgdat(page); > - bool locked; > + if (locked_lruvec) { > + if (lruvec_holds_page_lru_lock(page, locked_lruvec)) > + return locked_lruvec; > > - rcu_read_lock(); > - locked = mem_cgroup_page_lruvec(page, pgdat) == locked_lruvec; > - rcu_read_unlock(); > - > - if (locked) > - return locked_lruvec; > - > - if (locked_lruvec) > unlock_page_lruvec_irq(locked_lruvec); > + } > > return lock_page_lruvec_irq(page); > } > @@ -1337,18 +1355,12 @@ static inline struct lruvec *relock_page_lruvec_irq(struct page *page, > static inline struct lruvec *relock_page_lruvec_irqsave(struct page *page, > struct lruvec *locked_lruvec, unsigned long *flags) > { > - struct pglist_data *pgdat = page_pgdat(page); > - bool locked; > - > - rcu_read_lock(); > - locked = mem_cgroup_page_lruvec(page, pgdat) == locked_lruvec; > - rcu_read_unlock(); > - > - if (locked) > - return locked_lruvec; > + if (locked_lruvec) { > + if (lruvec_holds_page_lru_lock(page, locked_lruvec)) > + return locked_lruvec; > > - if (locked_lruvec) > unlock_page_lruvec_irqrestore(locked_lruvec, *flags); > + } > > return lock_page_lruvec_irqsave(page, flags); > } >