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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69E22C001DC for ; Mon, 31 Jul 2023 12:00:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231321AbjGaMAz (ORCPT ); Mon, 31 Jul 2023 08:00:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230177AbjGaMAx (ORCPT ); Mon, 31 Jul 2023 08:00:53 -0400 Received: from out30-112.freemail.mail.aliyun.com (out30-112.freemail.mail.aliyun.com [115.124.30.112]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6DA95B5 for ; Mon, 31 Jul 2023 05:00:52 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046050;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0Vog4uW9_1690804847; Received: from 30.97.48.66(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0Vog4uW9_1690804847) by smtp.aliyun-inc.com; Mon, 31 Jul 2023 20:00:48 +0800 Message-ID: <6e76323f-a1cc-7d20-676e-4eccdbcf6b91@linux.alibaba.com> Date: Mon, 31 Jul 2023 20:01:15 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH 1/8] mm/compaction: avoid missing last page block in section after skip offline sections To: Kemeng Shi , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mgorman@techsingularity.net, willy@infradead.org, david@redhat.com References: <20230728171037.2219226-1-shikemeng@huaweicloud.com> <20230728171037.2219226-2-shikemeng@huaweicloud.com> From: Baolin Wang In-Reply-To: <20230728171037.2219226-2-shikemeng@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/29/2023 1:10 AM, Kemeng Shi wrote: > skip_offline_sections_reverse will return the last pfn in found online > section. Then we set block_start_pfn to start of page block which > contains the last pfn in section. Then we continue, move one page > block forward and ignore the last page block in the online section. > Make block_start_pfn point to first page block after online section to fix > this: > 1. make skip_offline_sections_reverse return end pfn of online section, > i.e. pfn of page block after online section. > 2. assign block_start_pfn with next_pfn. > > Fixes: f63224525309 ("mm: compaction: skip the memory hole rapidly when isolating free pages") > Signed-off-by: Kemeng Shi > --- > mm/compaction.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 9b7a0a69e19f..ce7841363b12 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -259,7 +259,7 @@ static unsigned long skip_offline_sections_reverse(unsigned long start_pfn) > > while (start_nr-- > 0) { > if (online_section_nr(start_nr)) > - return section_nr_to_pfn(start_nr) + PAGES_PER_SECTION - 1; > + return section_nr_to_pfn(start_nr + 1); This is incorrect, you returned the start pfn of this section. > } > > return 0; > @@ -1670,8 +1670,7 @@ static void isolate_freepages(struct compact_control *cc) > > next_pfn = skip_offline_sections_reverse(block_start_pfn); > if (next_pfn) > - block_start_pfn = max(pageblock_start_pfn(next_pfn), > - low_pfn); > + block_start_pfn = max(next_pfn, low_pfn); 'block_start_pfn' should be pageblock aligned. If the 'next_pfn' is not pageblock-aligned (though this is not the common case), we should skip it. But if the 'next_pfn' is pageblock-aligned, yes, the commit f63224525309 still ignores the last pageblock, which is not right. So I think it should be: block_start_pfn = pageblock_aligned(next_pfn) ? : pageblock_start_pfn(next_pfn); block_start_pfn = max(block_start_pfn, low_pfn);