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=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 BB38BC4363A for ; Fri, 30 Oct 2020 14:49:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B88722210 for ; Fri, 30 Oct 2020 14:49:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="j+ISWsOZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727034AbgJ3OtU (ORCPT ); Fri, 30 Oct 2020 10:49:20 -0400 Received: from mx2.suse.de ([195.135.220.15]:59112 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726596AbgJ3OtT (ORCPT ); Fri, 30 Oct 2020 10:49:19 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1604069358; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=jC196offWe8kZaKf5Rpbbnzmhqts/gI7NsBHR/i23IY=; b=j+ISWsOZGJGLNKcv59Kl8bfKr0BHSQ3sw34cw5g0O/yq3SJfwO498lNZmdrf2z/7YCc9Vq GcVXPCUTNzvomOIqAKgfQ/R3wBxU7K/vbWgugsCbQQVMsH3mth+gOOIK/gi6ACd5PyxpFZ d0idin88Iu2Z+XwNiLrEwR9HbnYTRM0= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0D118AF0B; Fri, 30 Oct 2020 14:49:18 +0000 (UTC) Date: Fri, 30 Oct 2020 15:49:17 +0100 From: Michal Hocko To: Zi Yan Cc: Andrew Morton , linux-mm@kvack.org, Rik van Riel , linux-kernel@vger.kernel.org, Vlastimil Babka Subject: Re: [PATCH] mm/compaction: count pages and stop correctly during page isolation. Message-ID: <20201030144917.GK1478@dhcp22.suse.cz> References: <20201029200435.3386066-1-zi.yan@sent.com> <20201030094308.GG1478@dhcp22.suse.cz> <6CAAB1FC-2B41-490B-A67A-93063629C19B@nvidia.com> <20201030133625.GJ1478@dhcp22.suse.cz> <400B3460-65C0-4C48-A7EA-1A9F5780EC9C@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <400B3460-65C0-4C48-A7EA-1A9F5780EC9C@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 30-10-20 10:35:43, Zi Yan wrote: > On 30 Oct 2020, at 9:36, Michal Hocko wrote: > > > On Fri 30-10-20 08:20:50, Zi Yan wrote: > >> On 30 Oct 2020, at 5:43, Michal Hocko wrote: > >> > >>> [Cc Vlastimil] > >>> > >>> On Thu 29-10-20 16:04:35, Zi Yan wrote: > >>>> From: Zi Yan > >>>> > >>>> In isolate_migratepages_block, when cc->alloc_contig is true, we are > >>>> able to isolate compound pages, nr_migratepages and nr_isolated did not > >>>> count compound pages correctly, causing us to isolate more pages than we > >>>> thought. Use thp_nr_pages to count pages. Otherwise, we might be trapped > >>>> in too_many_isolated while loop, since the actual isolated pages can go > >>>> up to COMPACT_CLUSTER_MAX*512=16384, where COMPACT_CLUSTER_MAX is 32, > >>>> since we stop isolation after cc->nr_migratepages reaches to > >>>> COMPACT_CLUSTER_MAX. > >>>> > >>>> In addition, after we fix the issue above, cc->nr_migratepages could > >>>> never be equal to COMPACT_CLUSTER_MAX if compound pages are isolated, > >>>> thus page isolation could not stop as we intended. Change the isolation > >>>> stop condition to >=. > >>>> > >>>> Signed-off-by: Zi Yan > >>>> --- > >>>> mm/compaction.c | 8 ++++---- > >>>> 1 file changed, 4 insertions(+), 4 deletions(-) > >>>> > >>>> diff --git a/mm/compaction.c b/mm/compaction.c > >>>> index ee1f8439369e..0683a4999581 100644 > >>>> --- a/mm/compaction.c > >>>> +++ b/mm/compaction.c > >>>> @@ -1012,8 +1012,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, > >>>> > >>>> isolate_success: > >>>> list_add(&page->lru, &cc->migratepages); > >>>> - cc->nr_migratepages++; > >>>> - nr_isolated++; > >>>> + cc->nr_migratepages += thp_nr_pages(page); > >>>> + nr_isolated += thp_nr_pages(page); > >>> > >>> Does thp_nr_pages work for __PageMovable pages? > >> > >> Yes. It is the same as compound_nr() but compiled > >> to 1 when THP is not enabled. > > > > I am sorry but I do not follow. First of all the implementation of the > > two is different and also I was asking about __PageMovable which should > > never be THP IIRC. Can they be compound though? > > __PageMovable, non-lru movable pages, can be compound and thp_nr_page cannot > be used for it, since when THP is off, thp_nr_page will return the wrong number. > I got confused by its name, sorry. OK, this matches my understanding. Good we are on the same page. > But __PageMovable is irrelevant to this patch, since we are using > __isolate_lru_page to isolate pages. non-lru __PageMovable should not appear > after isolate_succes. thp_nr_pages can be used here. But this is still not clear to me. __PageMovable pages are isolated by isolate_movable_page and then jump to isolate_succes. Does that somehow changes the nature of the page being compound or tat thp_nr_page would start working on those pages. -- Michal Hocko SUSE Labs