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[2003:cb:c706:6b00:bf49:f14b:380d:f871]) by smtp.gmail.com with ESMTPSA id i8-20020adfefc8000000b0030ada01ca78sm4495010wrp.10.2023.07.28.03.41.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Jul 2023 03:41:05 -0700 (PDT) Message-ID: <8d3f4a1d-b624-3e2f-653c-032833646dea@redhat.com> Date: Fri, 28 Jul 2023 12:41:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; 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, baolin.wang@linux.alibaba.com, mgorman@techsingularity.net, willy@infradead.org References: <20230728171037.2219226-1-shikemeng@huaweicloud.com> <20230728171037.2219226-2-shikemeng@huaweicloud.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230728171037.2219226-2-shikemeng@huaweicloud.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4755F40022 X-Stat-Signature: ydfwwwccu9s5wpyr1tfrpwrqwn1qect6 X-Rspam-User: X-HE-Tag: 1690540870-353203 X-HE-Meta: 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 1iCfIkzi 2g0XH64qZll8HA9z9q5o7dFFEKm5WmEHnkxVfDMryLDy5hR8/8sa8qXQcSYdyKzHMFB53PEHGx6WRBNDoSvzUfG9zF71a2ikJYTqj1FoaLrH14CYZbq6YSdtANYJntpDE/ykzygykBtAOhkg+o7JSM9tutyeaFlNmF823/xFryVaecyyHR4a+vCek3du81mxgLOpu31HR3VhInkVxE0uM2r30X4g1dpUTxibdypuv4xAsN99G0TrxZc/mgRt2b7c2nq0Xho6PbCtPt5FfEd+D5pL+1Bf/NZ+LdO5zV86ePScdW1aZ9nvIj7YY359BukRZoQ4vherLvewqE6TUD5NJ2BZZALSf6EyFnl7C/EIpSYqfnyLxLE6lmN/+xWJCFyRvdB46EB3yNiv73CZAmqWtFYlNwOEnLmAyECCit1S/v57Ip4f3YN4qWLQjbA== 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 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)? > @@ -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 :) -- Cheers, David / dhildenb