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 F3B0BC001DE for ; Tue, 1 Aug 2023 02:36:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231272AbjHACg2 (ORCPT ); Mon, 31 Jul 2023 22:36:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35382 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229987AbjHACgY (ORCPT ); Mon, 31 Jul 2023 22:36:24 -0400 Received: from dggsgout12.his.huawei.com (unknown [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A04E2F1 for ; Mon, 31 Jul 2023 19:36:06 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4RFK3h2t5Lz4f3jMg for ; Tue, 1 Aug 2023 10:36:00 +0800 (CST) Received: from [10.174.178.129] (unknown [10.174.178.129]) by APP1 (Coremail) with SMTP id cCh0CgBXsRuRb8hkTSf1OQ--.1427S2; Tue, 01 Aug 2023 10:36:02 +0800 (CST) Subject: Re: [PATCH 1/8] mm/compaction: avoid missing last page block in section after skip offline sections From: Kemeng Shi To: Baolin Wang , 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> <6e76323f-a1cc-7d20-676e-4eccdbcf6b91@linux.alibaba.com> <9b207dbf-1652-4851-7c6e-16220d5f2f3b@huaweicloud.com> Message-ID: Date: Tue, 1 Aug 2023 10:36:01 +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: <9b207dbf-1652-4851-7c6e-16220d5f2f3b@huaweicloud.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-CM-TRANSID: cCh0CgBXsRuRb8hkTSf1OQ--.1427S2 X-Coremail-Antispam: 1UD129KBjvJXoWxCw1kCw48Jry3uw1rCw1xXwb_yoW5tFyrpr yxJFy2gryDG348Wa4xtw1kuryjyws5Ga1UXr47JF18AF1DXFn2gFyqqr1q9ryjgrWxAFyU Zr40yFW7Zr17A37anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUk0b4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JMxk0xIA0c2IEe2xFo4CEbIxvr21l42xK82IYc2Ij 64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x 8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r126r1DMIIYrxkI7VAKI48JMIIF0xvE 2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r1j6r4UMIIF0xvE42 xK8VAvwI8IcIk0rVWrJr0_WFyUJwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv 6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjxUrR6zUUUUU X-CM-SenderInfo: 5vklyvpphqwq5kxd4v5lfo033gof0z/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org on 8/1/2023 10:18 AM, Kemeng Shi wrote: > > > on 7/31/2023 8:01 PM, Baolin Wang wrote: >> >> >> 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); >> > Hi Baolin, thanks for reply! As skip_offline_sections_reverse is based > on skip_offline_sections. I make the assumption that section is pageblock > aligned based on that we use section start from skip_offline_sections as > block_start_fpn without align check. > If section size is not pageblock aligned in real world, the pageblock aligned > check should be added to skip_offline_sections and skip_offline_sections_reverse. > If no one is against this, I will fix this in next version. THanks! > More information of aligment of section. For powerpc arch, we have SECTION_SIZE_BITS with 24 while PAGE_SHIFT could be configured to 18. Pageblock order is (18 + MAX_ORDER) which coule be 28 and is > SECTION_SZIE_BITS 24, then section start is not aligned with pageblock size. Please correct me if I miss anything. Thanks! -- Best wishes Kemeng Shi