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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 3EE1CC4741F for ; Thu, 5 Nov 2020 08:56:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BCBA6206FB for ; Thu, 5 Nov 2020 08:56:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BCBA6206FB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 4945B6B00A6; Thu, 5 Nov 2020 03:56:18 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 41FDD6B00A7; Thu, 5 Nov 2020 03:56:18 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1AB526B00A8; Thu, 5 Nov 2020 03:56:18 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0196.hostedemail.com [216.40.44.196]) by kanga.kvack.org (Postfix) with ESMTP id DAADA6B00A6 for ; Thu, 5 Nov 2020 03:56:17 -0500 (EST) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 7E2163D15 for ; Thu, 5 Nov 2020 08:56:17 +0000 (UTC) X-FDA: 77449757994.17.twig78_500bc2b272c8 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id 665E1180D0181 for ; Thu, 5 Nov 2020 08:56:17 +0000 (UTC) X-HE-Tag: twig78_500bc2b272c8 X-Filterd-Recvd-Size: 3369 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by imf46.hostedemail.com (Postfix) with ESMTP for ; Thu, 5 Nov 2020 08:56:15 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R671e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=23;SR=0;TI=SMTPD_---0UEJC3Fv_1604566567; Received: from aliy80.localdomain(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0UEJC3Fv_1604566567) by smtp.aliyun-inc.com(127.0.0.1); Thu, 05 Nov 2020 16:56:11 +0800 From: Alex Shi To: akpm@linux-foundation.org, mgorman@techsingularity.net, tj@kernel.org, hughd@google.com, khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com, willy@infradead.org, hannes@cmpxchg.org, lkp@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, shakeelb@google.com, iamjoonsoo.kim@lge.com, richard.weiyang@gmail.com, kirill@shutemov.name, alexander.duyck@gmail.com, rong.a.chen@intel.com, mhocko@suse.com, vdavydov.dev@gmail.com, shy828301@gmail.com Cc: Vlastimil Babka , Minchan Kim Subject: [PATCH v21 07/19] mm: page_idle_get_page() does not need lru_lock Date: Thu, 5 Nov 2020 16:55:37 +0800 Message-Id: <1604566549-62481-8-git-send-email-alex.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1604566549-62481-1-git-send-email-alex.shi@linux.alibaba.com> References: <1604566549-62481-1-git-send-email-alex.shi@linux.alibaba.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Hugh Dickins It is necessary for page_idle_get_page() to recheck PageLRU() after get_page_unless_zero(), but holding lru_lock around that serves no useful purpose, and adds to lru_lock contention: delete it. See https://lore.kernel.org/lkml/20150504031722.GA2768@blaptop for the discussion that led to lru_lock there; but __page_set_anon_rmap() now uses WRITE_ONCE(), and I see no other risk in page_idle_clear_pte_refs() using rmap_walk() (beyond the risk of racing PageAnon->PageKsm, mostly but not entirely prevented by page_count() check in ksm.c's write_protect_page(): that risk being shared with page_referenced() and not helped by lru_lock). Signed-off-by: Hugh Dickins Signed-off-by: Alex Shi Cc: Andrew Morton Cc: Vladimir Davydov Cc: Vlastimil Babka Cc: Minchan Kim Cc: Alex Shi Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- mm/page_idle.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/mm/page_idle.c b/mm/page_idle.c index 057c61df12db..64e5344a992c 100644 --- a/mm/page_idle.c +++ b/mm/page_idle.c @@ -32,19 +32,15 @@ static struct page *page_idle_get_page(unsigned long pfn) { struct page *page = pfn_to_online_page(pfn); - pg_data_t *pgdat; if (!page || !PageLRU(page) || !get_page_unless_zero(page)) return NULL; - pgdat = page_pgdat(page); - spin_lock_irq(&pgdat->lru_lock); if (unlikely(!PageLRU(page))) { put_page(page); page = NULL; } - spin_unlock_irq(&pgdat->lru_lock); return page; } -- 1.8.3.1