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=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL 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 F0546C43464 for ; Fri, 18 Sep 2020 10:27:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF38921D24 for ; Fri, 18 Sep 2020 10:27:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="BfSusiEE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726416AbgIRK1X (ORCPT ); Fri, 18 Sep 2020 06:27:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46672 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726253AbgIRK1X (ORCPT ); Fri, 18 Sep 2020 06:27:23 -0400 Received: from mail-il1-x141.google.com (mail-il1-x141.google.com [IPv6:2607:f8b0:4864:20::141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4C993C061756 for ; Fri, 18 Sep 2020 03:27:23 -0700 (PDT) Received: by mail-il1-x141.google.com with SMTP id y9so5750235ilq.2 for ; Fri, 18 Sep 2020 03:27:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=NGiEMA4XCl4K+615B920D7aQUry3FhMY/+Djt+whFqk=; b=BfSusiEEsa1NXeEVIhqZLCV1KtYitRimBhpYQvTDRPjZwA8Niznd44p/mt3fvgqz92 TyOI3sUfqBAVzIA5ZyjIsM2Jnv91UbxibfyvI8MEQKlG9rlIkdCILCx3qb6dANANbQMu C9JT8sDI4gKJXulouBx0u0liWJiAy6/Uhjzs+V8dLiXmMZXTA0q36Ze0BOJZ5S0dJoZ/ 8gocaTvRbHYOvwKYUNbv6uqH+NPCoJnyojRoATvIc5O5eFSHoFNjU34njF/nJItwsu/B uQaCvVr40K27xwOrYgP8X15+qCP8KWx/kVTgTnWbPwj2D+8poiRAcoOFCG11iH5fIB/0 8BOg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=NGiEMA4XCl4K+615B920D7aQUry3FhMY/+Djt+whFqk=; b=bv9NoLmINYZ9WvfCuzoKGTObeQxng7Argb5K6x7JbpMWyxLeO7H6QwqTSVyvxNJA0y 9bBUnJ+tLikpPQt3fCvLL7lGnh8vMl9JPMQkceyAF8kduSHAWt84ZmhX733HQ3Cjdz2z +TFU6HDWK1WXtbsjh1ZhBNJdChT6mb1Oy8gcTwONzVo/N3utBN49aTi05VuJ3OAOZwWW 0Exb34JBxE+kOurqgUqnFzaYbG1HCsgtP3E4bPd28DPeq/Q0VwHda8ldQdlxqcx30/Un gBVoTUvmMJ2iaHGW8j0TGHxLPJyXAxCmmZ1G16ih3uzb+EZrFnP7hnpDigLOBj5JbbAD hYsQ== X-Gm-Message-State: AOAM531QXs7Eai0cl4PGpNgNgG1Fu/OwnbaUwFk9veOM2+ldOLEizj5P 6B8nIHzQ6fe3IIAlz3vF2+q2ww== X-Google-Smtp-Source: ABdhPJxD0fEoDDQySb9R9MBT2QbJBYq3F8vY/USPXDVLW8g54ZvBe7hDoB8Np6nohaIm2+1S9MjsUg== X-Received: by 2002:a92:98c5:: with SMTP id a66mr29173637ill.50.1600424842237; Fri, 18 Sep 2020 03:27:22 -0700 (PDT) Received: from google.com ([2620:15c:183:200:7220:84ff:fe09:2d90]) by smtp.gmail.com with ESMTPSA id i14sm1422014ilb.28.2020.09.18.03.27.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2020 03:27:20 -0700 (PDT) Date: Fri, 18 Sep 2020 04:27:13 -0600 From: Yu Zhao To: Michal Hocko Cc: Andrew Morton , Alex Shi , Steven Rostedt , Ingo Molnar , Johannes Weiner , Vladimir Davydov , Roman Gushchin , Shakeel Butt , Chris Down , Yafang Shao , Vlastimil Babka , Huang Ying , Pankaj Gupta , Matthew Wilcox , Konstantin Khlebnikov , Minchan Kim , Jaewon Kim , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 02/13] mm: use page_off_lru() Message-ID: <20200918102713.GB1004594@google.com> References: <20200918030051.650890-1-yuzhao@google.com> <20200918030051.650890-3-yuzhao@google.com> <20200918073700.GE28827@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200918073700.GE28827@dhcp22.suse.cz> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 18, 2020 at 09:37:00AM +0200, Michal Hocko wrote: > On Thu 17-09-20 21:00:40, Yu Zhao wrote: > > This patch replaces the only open-coded __ClearPageActive() with > > page_off_lru(). There is no open-coded __ClearPageUnevictable()s. > > > > Before this patch, we have: > > __ClearPageActive() > > add_page_to_lru_list() > > > > After this patch, we have: > > page_off_lru() > > if PageUnevictable() > > __ClearPageUnevictable() > > else if PageActive() > > __ClearPageActive() > > add_page_to_lru_list() > > > > Checking PageUnevictable() shouldn't be a problem because these two > > flags are mutually exclusive. Leaking either will trigger bad_page(). > > I am sorry but the changelog is really hard to grasp. What are you > trying to achieve, why and why it is safe. This should be a general > outline for any patch. I have already commented on the previous patch > and asked you for the explanation why removing __ClearPageActive from > this path is desirable and safe. I have specifically asked to clarify > the compound page situation as that is using its oen destructor in the > freeing path and that might result in page_off_lru to be not called. Haven't I explained we are NOT removing __ClearPageActive()? Is my notion of the code structure above confusing you? Or 'open-coded' could mean different things? And I have asked this before: why does 'the compound page situation' even matter here? Perhaps if you could give a concrete example related to the code change and help me understand your concern? > > Signed-off-by: Yu Zhao > > --- > > mm/vmscan.c | 6 +----- > > 1 file changed, 1 insertion(+), 5 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 503fc5e1fe32..f257d2f61574 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -1845,7 +1845,6 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec, > > int nr_pages, nr_moved = 0; > > LIST_HEAD(pages_to_free); > > struct page *page; > > - enum lru_list lru; > > > > while (!list_empty(list)) { > > page = lru_to_page(list); > > @@ -1860,14 +1859,11 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec, > > lruvec = mem_cgroup_page_lruvec(page, pgdat); > > > > SetPageLRU(page); > > - lru = page_lru(page); > > - > > add_page_to_lru_list(page, lruvec, lru); > > > > if (put_page_testzero(page)) { > > __ClearPageLRU(page); > > - __ClearPageActive(page); > > - del_page_from_lru_list(page, lruvec, lru); > > + del_page_from_lru_list(page, lruvec, page_off_lru(page)); > > > > if (unlikely(PageCompound(page))) { > > spin_unlock_irq(&pgdat->lru_lock); > > -- > > 2.28.0.681.g6f77f65b4e-goog > > -- > Michal Hocko > SUSE Labs