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 814AEEB64DD for ; Sat, 29 Jul 2023 02:23:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231254AbjG2CXr (ORCPT ); Fri, 28 Jul 2023 22:23:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229498AbjG2CXp (ORCPT ); Fri, 28 Jul 2023 22:23:45 -0400 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E7201BC1 for ; Fri, 28 Jul 2023 19:23:44 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.143]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4RCSwn5sLcz4f3kjG for ; Sat, 29 Jul 2023 10:23:37 +0800 (CST) Received: from [10.174.178.129] (unknown [10.174.178.129]) by APP4 (Coremail) with SMTP id gCh0CgC3h64reMRkx2Q4PA--.18707S2; Sat, 29 Jul 2023 10:23:40 +0800 (CST) Subject: Re: [PATCH 1/8] mm/compaction: avoid missing last page block in section after skip offline sections To: David Hildenbrand , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, baolin.wang@linux.alibaba.com, mgorman@techsingularity.net, willy@infradead.org References: <20230728171037.2219226-1-shikemeng@huaweicloud.com> <20230728171037.2219226-2-shikemeng@huaweicloud.com> <8d3f4a1d-b624-3e2f-653c-032833646dea@redhat.com> From: Kemeng Shi Message-ID: Date: Sat, 29 Jul 2023 10:23:38 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <8d3f4a1d-b624-3e2f-653c-032833646dea@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-CM-TRANSID: gCh0CgC3h64reMRkx2Q4PA--.18707S2 X-Coremail-Antispam: 1UD129KBjvJXoW7ZF4fJF15JFyxuryfKFW3KFg_yoW8KFyUpr 48JFy7GryDX348Wa40yw1Uuryjyrs5Ja1UJr47AF18AF15Xr10gF92qr1q9r1jgrWxAFyj yr1vyFZruw13ArDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUyEb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JMxk0xIA0c2IEe2xFo4CEbIxvr21l42xK82IYc2Ij 64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x 8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r126r1DMIIYrxkI7VAKI48JMIIF0xvE 2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r1j6r4UMIIF0xvE42 xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIE c7CjxVAFwI0_Jr0_GrUvcSsGvfC2KfnxnUUI43ZEXa7IU1zuWJUUUUU== X-CM-SenderInfo: 5vklyvpphqwq5kxd4v5lfo033gof0z/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org on 7/28/2023 6:41 PM, David Hildenbrand wrote: > On 28.07.23 19:10, 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 > > Can we add a short comment which kind of PFN we return (first pfn of first offline section after an online section)? > Hi David, thanks for the review. Sure, I will add comment to skip_offline_sections_reverse. -- Best wishes Kemeng Shi >> @@ -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); >>       } >>         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); > > > So block_start_pfn() will now point at the first PFN of the offline section. > > Confusing stuff, but I get the idea and I think it makes sense to me :) >