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Thu, 01 Oct 2026 18:25:29 -0700 (PDT) From: Qiliang Yuan Subject: [PATCH v2 0/2] mm/migrate: speed up move_pages() node queries Date: Fri, 02 Oct 2026 09:25:25 +0800 Message-Id: <20261002-bug-mm-move-pages-stat-batch-v2-0-f73b5d20519f@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAAUIv2oC/43NQQ6CMBCF4auQrh1DGwriynsYFgMOZRJLSVsbD endrZzA5fcW/9tFIM8UxLXahafEgd1aoE6VmBZcDQE/ioWqVSvrWsL4MmAtWJcINjQUIESMMGK cFphbhaon1Je2EyWxeZr5feTvQ/HCITr/Od6S/K1/hpMECUrrsaNe6q5pbsYiP8+Ts2LIOX8BM hftjMgAAAA= To: Andrew Morton , David Hildenbrand , Zi Yan , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qiliang Yuan X-Mailer: b4 0.13.0 move_pages() with a NULL node list reports the node of each page, and RDMA and KV-cache engines call it on every page of buffers spanning hundreds of gigabytes. do_pages_stat_array() walks the page tables from the top for every address, at about 105 ns per page. Patch 1 walks runs of consecutive pages with walk_page_range(). Patch 2 raises the do_pages_stat() chunk from 16 to 512 pages so that a run can cover a whole PTE table. Together they bring the per-page cost from 104 ns to 12.3 ns with 4K pages and from 90.6 ns to 2.0 ns with THP, and a 16 GiB buffer of 4K pages from 486 ms to 52 ms. Signed-off-by: Qiliang Yuan --- V1 -> V2: - Walk the runs with walk_page_range() and a pmd_entry callback instead of extending folio_walk_start() by hand (Zi Yan) - Raise DO_PAGES_STAT_CHUNK_NR from 16 to 512 in a separate patch, with numbers for each chunk size (Zi Yan) - Re-measure everything in one run on a VM that now has two NUMA nodes, with the test bound to CPU 0, so the baselines differ from v1 (16 GiB of 4K pages: 486 ms instead of 440 ms) v1: https://lore.kernel.org/r/20261001-bug-mm-move-pages-stat-batch-v1-1-255b7e915744@gmail.com --- Qiliang Yuan (2): mm/migrate: walk runs of consecutive pages in do_pages_stat_array() mm/migrate: raise the do_pages_stat() chunk to 512 pages mm/migrate.c | 206 ++++++++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 177 insertions(+), 29 deletions(-) --- base-commit: 551c722f40809618230001baccf219193e22fc5a change-id: 20261001-bug-mm-move-pages-stat-batch-f62a29ea5867 Best regards, -- Qiliang Yuan