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rv:102.0) Gecko/20100101 Thunderbird/102.14.0 Subject: Re: [PATCH 4/9] mm/compaction: simplify pfn iteration in isolate_freepages_range To: Kemeng Shi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mgorman@techsingularity.net, david@redhat.com References: <20230805110711.2975149-1-shikemeng@huaweicloud.com> <20230805110711.2975149-5-shikemeng@huaweicloud.com> From: Baolin Wang In-Reply-To: <20230805110711.2975149-5-shikemeng@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 5170E40007 X-Stat-Signature: 8jhzrhh1g9j4b8brz5shx1kfnz1fx7ku X-HE-Tag: 1692088727-203668 X-HE-Meta: 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 9RdZO8fw IxNUNxpRrAC8qGpYQSHpcTrzI+9q7Oc3X9CVibY8G/6Uk4zB3lwZbEQZvfDsTIE9dErFzdYwGJiX4aSR53x8C2zPMM0sJaGgy4D72VTjoevz91Pe8Fy0OVNMwXQ58awYMv+rmTcjIuuuCW74belN9QUWZWFWo8RDb/E5A8uxcIMoAlu9X+1+tpu91Mw== 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 8/5/2023 7:07 PM, Kemeng Shi wrote: > We call isolate_freepages_block in strict mode, continuous pages in > pageblock will be isolated if isolate_freepages_block successed. > Then pfn + isolated will point to start of next pageblock to scan > no matter how many pageblocks are isolated in isolate_freepages_block. > Use pfn + isolated as start of next pageblock to scan to simplify the > iteration. IIUC, the isolate_freepages_block() can isolate high-order free pages, which means the pfn + isolated can be larger than the block_end_pfn. So in your patch, the 'block_start_pfn' and 'block_end_pfn' can be in different pageblocks, that will break pageblock_pfn_to_page(). > > Signed-off-by: Kemeng Shi > --- > mm/compaction.c | 14 ++------------ > 1 file changed, 2 insertions(+), 12 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 684f6e6cd8bc..8d7d38073d30 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -733,21 +733,11 @@ isolate_freepages_range(struct compact_control *cc, > block_end_pfn = pageblock_end_pfn(pfn); > > for (; pfn < end_pfn; pfn += isolated, > - block_start_pfn = block_end_pfn, > - block_end_pfn += pageblock_nr_pages) { > + block_start_pfn = pfn, > + block_end_pfn = pfn + pageblock_nr_pages) { > /* Protect pfn from changing by isolate_freepages_block */ > unsigned long isolate_start_pfn = pfn; > > - /* > - * pfn could pass the block_end_pfn if isolated freepage > - * is more than pageblock order. In this case, we adjust > - * scanning range to right one. > - */ > - if (pfn >= block_end_pfn) { > - block_start_pfn = pageblock_start_pfn(pfn); > - block_end_pfn = pageblock_end_pfn(pfn); > - } > - > block_end_pfn = min(block_end_pfn, end_pfn); > > if (!pageblock_pfn_to_page(block_start_pfn,