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([23.254.208.9]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-34f14f2dfbbsm1942238eec.10.2026.10.01.18.27.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Oct 2026 18:27:42 -0700 (PDT) From: Qiliang Yuan To: Zi Yan Cc: Andrew Morton , David Hildenbrand , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/migrate: look up consecutive pages together in do_pages_stat_array() Date: Fri, 2 Oct 2026 09:27:37 +0800 Message-ID: <20261002012737.149491-1-odys.yuan@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <4CCA725B-9CFE-4ADF-AE8A-59D6ECA4321F@nvidia.com> References: <20261001-bug-mm-move-pages-stat-batch-v1-1-255b7e915744@gmail.com> <4CCA725B-9CFE-4ADF-AE8A-59D6ECA4321F@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: feicx8udmqayekmnzsca7cd97s5nq5kq X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 859501C0004 X-HE-Tag: 1790904464-917213 X-HE-Meta: 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 LaVR9EGE S8g8EPM7IpuAsKw4WZAoAhl4iItBZ4KLF68Uzmaf4bhK7cpRu1dZ0obCcdsMz6vH2c8WIWoRxQeEVdGvgfLzbSK8ZFIvch2h418pRZj7h7ygEyTLfthsVItF3R1WyHFbQLTfJ6GoZ0nTFvqcMKIGUWYddFhn3WtmSyJPoJ/7rJ2QEUuHhPXS2TaHmC7p4WslZoJf3MIepYSFvGROZWL3vz0830C0GU71btALEndGoFThtSg4RwK/AcbEO3IouMZD/7EoA534EWAdHTT5sYmgbqlIqIx7scRjh/RByQHCWtM56kYSUyvvDyUtMZNQ5Q6XzneHQqBmN7AoWdXkosI43alXVrew1TjrqwoGauIbO0UPmimx6J5XTRlVqDFtxabxEatkQu+8DMdsjyDs5pWClt4bBw+mf7+pEELL3SVcQwEUga/47PKGBNypwBZzmRJge73VNf6xFxEDzL1Vo+MQOR7ISIw/3BuHw2D4pLMgOxFbMLSDab8jJybDvmYnLiyc94FtAXU8a6uiAAgPYWG282bZHoBu0t+w5/TF5OWpn/LDxqdLMOszR0jqXhDEt75kXpkvRyUi5BcJywzJnYQHmfyE+fH5nKYJHmoI0 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1 Oct 2026, at 11:37, Zi Yan wrote: > Instead of adding customized batched walk code, it might be better to use > walk_page_range() + pmd_entry callback. See mincore_pte_range() for > reference. Thanks, v2 does that, with pud_entry and hugetlb_entry callbacks so the walk doesn't split PUD or hugetlb leaves. > BTW, DO_PAGES_STAT_CHUNK_NR is limited at 16, so the batching benefit > comes from 16 pages instead of 512 pages in one PMD? I wonder if that > limit could be raised and how much more benefit we will see. Yes. With runs walked in one go, the walk setup paid every 16 pages dominates. Per page, querying a populated 4 GiB buffer: 16 64 256 512 1024 4K pages 31.9 ns 15.0 ns 11.8 ns 11.2 ns 10.9 ns THP 23.1 ns 6.6 ns 2.5 ns 1.8 ns 1.6 ns v2 raises the chunk to 512 in a separate patch, which also allocates the arrays instead of keeping 6 KiB on the stack: https://lore.kernel.org/r/20261002-bug-mm-move-pages-stat-batch-v2-0-f73b5d20519f@gmail.com Qiliang