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Mon, 12 Jan 2026 08:59:31 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id B25A2404AD; Mon, 12 Jan 2026 09:02:32 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemf100008.china.huawei.com (7.185.36.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 12 Jan 2026 09:02:31 +0800 Message-ID: <1f8d9e87-ffb7-4cf5-b408-90e576115402@huawei.com> Date: Mon, 12 Jan 2026 09:02:30 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] mm: page_alloc: optimize pfn_range_valid_contig() To: Andrew Morton CC: David Hildenbrand , Oscar Salvador , Muchun Song , , , , Zi Yan , Vlastimil Babka , Brendan Jackman , Johannes Weiner , Matthew Wilcox References: <20260110042111.1541894-1-wangkefeng.wang@huawei.com> <20260110042111.1541894-2-wangkefeng.wang@huawei.com> <20260110154327.6a723dc91c059ac219272bcb@linux-foundation.org> Content-Language: en-US From: Kefeng Wang In-Reply-To: <20260110154327.6a723dc91c059ac219272bcb@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: kwepems500002.china.huawei.com (7.221.188.17) To dggpemf100008.china.huawei.com (7.185.36.138) X-Stat-Signature: k7d8ieydnc39er4atfa4fawwhecstnjo X-Rspamd-Queue-Id: 48B9940007 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1768179757-46562 X-HE-Meta: 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 8ipCFKSc 6RZdrdn98jIfWi9G5cHKrl4uYFKoHHtF4RaLCbUH5M8fqkQpB4bxEhckPaIiQfqhM6z3kG0SpXo9IZhisrUOD9O/Yt5SIW24G20MB89sYo8Aom/EIuYtnCJsmX4+2dxB/aJDnLWL+dPDNhdI6bDJpaK8Krk3g9W7xP9M9bxSXTAnmgztWOxWx/QHIFnn3eXBenbzfFNAAmLe04ptwvI+LM4EDJKAcNlaGXPcz9lix8Nv9MzQyS0cnwuxgYOI9HjONwJUljj5AcQG0zdNUjq9qT7Xo8YzD00vvMNh2LdlwkXxq/jakfSIMZBr4Vev3s7nrevLMnzoo555F6e7e8w6tEBcD4hlrnCyPLnvLQeXbuGg+sn+WOPvciaE9E6hhqfSizjM+ 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: List-Subscribe: List-Unsubscribe: On 2026/1/11 7:43, Andrew Morton wrote: > On Sat, 10 Jan 2026 12:21:09 +0800 Kefeng Wang wrote: > >> The alloc_contig_pages() function spends a significant amount of time >> within the pfn_range_valid_contig() function. > > Trivia time: saying "the foo() function" is no more useful than simply > saying "foo()". "foo() spends a significant..." is shorter and causes > no information loss! Sure. > >> - set_max_huge_pages >> - 99.98% alloc_pool_huge_folio >> only_alloc_fresh_hugetlb_folio.isra.0 >> - alloc_contig_frozen_pages_noprof >> - 87.00% pfn_range_valid_contig >> pfn_to_online_page >> - 12.91% alloc_contig_frozen_range_noprof >> 4.51% replace_free_hugepage_folios >> - 4.02% prep_new_page >> prep_compound_page >> - 2.98% undo_isolate_page_range >> - 2.79% unset_migratetype_isolate >> - 2.75% __move_freepages_block_isolate >> 2.71% __move_freepages_block >> - 0.98% start_isolate_page_range >> 0.66% set_migratetype_isolate >> >> To optimize this process, implement a new helper page_is_unmovable(), >> which reuses the logic from has_unmovable_pages(). This function avoids >> unnecessary iterations for compound pages, such as THP, and non-compound >> high-order buddy pages, which significantly improving the efficiency of >> contiguous memory allocation. >> >> A simple test on machine with 114G free memory, allocate 120 * 1G >> HugeTLB folios(104 successfully returned), >> >> time echo 120 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages >> >> Before: 0m3.605s >> After: 0m0.602s > > Well dang, I'm surprised that the previous code was so bad. I found this when testing the previous patch(frozen gigantic folio allocation), The efficiency of traversing each pfn is too low. > > The patch does a lot of code movement, which makes it hard to see > what it actually does. Is it possible to split these apart? > move-stuff-around, then speed-stuff-up? OK, will split it. >