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=-11.2 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,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 09CBBC388F2 for ; Mon, 2 Nov 2020 13:04:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 84E5F223B0 for ; Mon, 2 Nov 2020 13:04:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 84E5F223B0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CE8A96B0073; Mon, 2 Nov 2020 08:04:01 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C99A76B0074; Mon, 2 Nov 2020 08:04:01 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B8A596B0075; Mon, 2 Nov 2020 08:04:01 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0246.hostedemail.com [216.40.44.246]) by kanga.kvack.org (Postfix) with ESMTP id 8A8BD6B0073 for ; Mon, 2 Nov 2020 08:04:01 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 1EA681EF2 for ; Mon, 2 Nov 2020 13:04:01 +0000 (UTC) X-FDA: 77439495882.10.pen80_160439d272b0 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin10.hostedemail.com (Postfix) with ESMTP id 687CA16A4B1 for ; Mon, 2 Nov 2020 13:04:00 +0000 (UTC) X-HE-Tag: pen80_160439d272b0 X-Filterd-Recvd-Size: 4247 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Mon, 2 Nov 2020 13:03:59 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2C106ABAE; Mon, 2 Nov 2020 13:03:59 +0000 (UTC) Subject: Re: [PATCH v3 1/2] mm/compaction: count pages and stop correctly during page isolation. To: Zi Yan , Andrew Morton , linux-mm@kvack.org Cc: Yang Shi , Michal Hocko , Rik van Riel , linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20201030183809.3616803-1-zi.yan@sent.com> From: Vlastimil Babka Message-ID: <839ec612-1494-c341-302e-585056b2abae@suse.cz> Date: Mon, 2 Nov 2020 14:03:58 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201030183809.3616803-1-zi.yan@sent.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10/30/20 7:38 PM, Zi Yan wrote: > From: Zi Yan >=20 > 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 w= e > thought. Count compound pages as the number of base pages they contain. > Otherwise, we might be trapped in too_many_isolated while loop, > since the actual isolated pages can go up to > COMPACT_CLUSTER_MAX*512=3D16384, where COMPACT_CLUSTER_MAX is 32, > since we stop isolation after cc->nr_migratepages reaches to > COMPACT_CLUSTER_MAX. >=20 > 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 >=3D. >=20 > The issue can be triggered as follows: > In a system with 16GB memory and an 8GB CMA region reserved by > hugetlb_cma, if we first allocate 10GB THPs and mlock them > (so some THPs are allocated in the CMA region and mlocked), reserving > 6 1GB hugetlb pages via > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages will get stuc= k > (looping in too_many_isolated function) until we kill either task. > With the patch applied, oom will kill the application with 10GB THPs an= d > let hugetlb page reservation finish. >=20 > Fixes: 1da2f328fa64 (=E2=80=9Cmm,thp,compaction,cma: allow THP migratio= n for CMA allocations=E2=80=9D) > Signed-off-by: Zi Yan > Reviewed-by: Yang Shi > Cc: Acked-by: Vlastimil Babka > --- > mm/compaction.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) >=20 > diff --git a/mm/compaction.c b/mm/compaction.c > index ee1f8439369e..3e834ac402f1 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1012,8 +1012,8 @@ isolate_migratepages_block(struct compact_control= *cc, unsigned long low_pfn, > =20 > isolate_success: > list_add(&page->lru, &cc->migratepages); > - cc->nr_migratepages++; > - nr_isolated++; > + cc->nr_migratepages +=3D compound_nr(page); > + nr_isolated +=3D compound_nr(page); > =20 > /* > * Avoid isolating too much unless this block is being > @@ -1021,7 +1021,7 @@ isolate_migratepages_block(struct compact_control= *cc, unsigned long low_pfn, > * or a lock is contended. For contention, isolate quickly to > * potentially remove one source of contention. > */ > - if (cc->nr_migratepages =3D=3D COMPACT_CLUSTER_MAX && > + if (cc->nr_migratepages >=3D COMPACT_CLUSTER_MAX && > !cc->rescan && !cc->contended) { > ++low_pfn; > break; > @@ -1132,7 +1132,7 @@ isolate_migratepages_range(struct compact_control= *cc, unsigned long start_pfn, > if (!pfn) > break; > =20 > - if (cc->nr_migratepages =3D=3D COMPACT_CLUSTER_MAX) > + if (cc->nr_migratepages >=3D COMPACT_CLUSTER_MAX) > break; > } > =20 >=20